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NCERT Exemplar · Class 9 · Science

Chapter 13: Why Do We Fall Ill?

Practice each question, then open the answer or worked solution.

Multiple-choice Questions

1 questions
Q1Written answer

Which one of the following is not a viral disease?

(a) Dengue

(b) AIDS

(c) Typhoid

(d) Influenza

Soln:

Answer is (c) Typhoid

Explanation:

Typhoid is caused by a bacterium called Salmonella typhi

2. Which one of the following is not a bacterial disease?

(a) Cholera

(b) Tuberculosis

(c) Anthrax

(d) Influenza

Soln:

Answer is (d) Influenza

Explanation:

Cholera is caused by Vibrio cholera

Tuberculosis is caused by Mycobacterium tuberculosis

Anthrax is caused by Bacillus anthracis.

Influenza is caused by the Influenza virus hence option d) is the right answer.

3. Which one of the following diseases is not transmitted by mosquitos?

(a) Brain fever

(b) Malaria

(c) Typhoid

(d) Dengue

Soln:

Answer is (c) Typhoid

Explanation:

Typhoid is transmitted through contaminated food and water.

4. Which one of the following diseases is not caused by bacteria?

(a) Typhoid

(b) Anthrax

(c) Tuberculosis

(d) Malaria

Soln:

Answer is (d) Malaria

Explanation:

Malaria is caused by protozoan called Plasmodium vivax hence d) is the right answer

5. Which one of the following diseases is caused by protozoans?

(a) Malaria

(b) Influenza

(c) AIDS

(d) Cholera

Soln:

Answer is (a) Malaria

Explanation:

Malaria is caused by protozoan Plasmodium vivax.

6. Which one of the following has a long term effect on the health of an individual?

(a) Common cold

(b) Chickenpox

(c) Chewing tobacco

(d) Stress

Soln:

Answer is (c) Chewing tobacco

Explanation:

Common cold and chicken pox are acute diseases which will not produce any long-term effects. Stress can be managed and will not have long-term effects. Chewing tobacco is dangerous as it produces long-term effects.

7. Which of the following can make you ill if you come in contact with an infected person?

(a) High blood pressure

(b) Genetic abnormalities

(c) Sneezing

(d) Blood cancer

Soln:

Answer is (c) Sneezing

Explanation:

Sneezing is a symptom of common and other respiratory diseases which are transmitted through inhalation of contaminated air. Other options provided in the question are not infectious disease; hence they are not transmitted through human contact.

8. AIDS cannot be transmitted by

(a) sexual contact

(b) hugs

(c) breast feeding

(d) blood transfusion

Soln:

Answer is (b) hugs

Explanation;

AIDS is transmitted by the exchange of body fluids. When we hug each other there cannot be an exchange of any body fluid hence AIDS cannot be transmitted by hugs.

9. Making anti-viral drugs is more difficult than making anti-bacterial medicines because

(a) viruses make use of host machinery

(b) viruses are on the border line of living and non-living

(c) viruses have very few biochemical mechanisms of their own

(d) viruses have a protein coat

Soln:

Answer is (c) viruses have very few biochemical mechanisms of their own

Explanation:

Antibacterial drugs stop certain biochemical reaction in the bacteria that kills the bacteria. But in viruses, there are a few biochemical processes which are difficult to target hence making anti-viral drugs is difficult.

10. Which one of the following causes kala-azar?

(a) Ascaris

(b) Trypanosoma

(c) Leishmania

(d) Bacteria

Soln:

Answer is (c) Leishmania

11. If you live in an overcrowded and poorly ventilated house, it is possible that you may suffer from which of the following diseases

(a) Cancer

(b) AIDS

(c) Air borne diseases

(d) Cholera

Soln:

Answer is (c) Airborne diseases

12. Which disease is not transmitted by mosquitoes?

(a) Dengue

(b) Malaria

(c) Brain fever or encephalitis

(d) Pneumonia

Soln:

Answer is (d) Pneumonia

Explanation:

Pneumonia is transmitted through the air and not mosquitos.

13. Which one of the following is not important for individual health?

(a) Living in clean space

(b) Good economic condition

(c) Social equality and harmony

(d) Living in a large and well-furnished house

Soln:

Answer is (d) Living in a large and well-furnished house

14. Choose the wrong statement

(a) High blood pressure is caused by excessive weight and lack of exercise.

(b) Cancers can be caused by genetic abnormalities

(c) Peptic ulcers are caused by eating acidic food

(d) Acne is not caused by staphylococci

Soln:

Answer is (d) Acne is not caused by staphylococci

Explanation:

Answer (d) is wrong because acne is a bacterial skin infection which is caused by staphylococci.

15. We should not allow mosquitoes to breed in our surroundings because they

(a) multiply very fast and cause pollution

(b) are vectors for many diseases

(c) bite and cause skin diseases

(d) are not important insects

Soln:

Answer is (b) are vectors for many diseases

Explanation:

Mosquitos are dangerous as they spread disease like Malaria, Dengue, Japanese encephalitis etc.

16. You are aware of Polio Eradication Programme in your city. Children are vaccinated because

(a) vaccination kills the polio-causing microorganisms

(b) prevents the entry of polio-causing organism

(c) it creates immunity in the body

(d) all the above

Soln:

Answer is (c) it creates immunity in the body

Explanation:

Vaccines create immunity against the pathogens against which it is designed.

17. Viruses, which cause hepatitis, are transmitted through

(a) air

(b) water

(c) food

(d) personal contact

Soln:

Answer is (b) water

18. Vectors can be defined as

(a) animals carrying the infecting agents from sick person to another healthy person

(b) microorganisms which cause many diseases

(c) infected person

(d) diseased plants

Soln:

Answer is (a) animals carrying the infecting agents from sick person to another healthy person.

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