Which one of the following is not an epidemic disease?
- A.Cholera
- B.Malaria
- C.Smallpox
- D.Elephantiasis
Correct answer
Explanation
The correct answer is D, Elephantiasis. Elephantiasis, or lymphatic filariasis, is an endemic disease: it stays steadily present in certain regions and develops slowly over years, rather than breaking out suddenly in a large number of people.
An epidemic is a sudden rise in cases of a disease in a community, well above what is normal. Elephantiasis is caused by the roundworm Wuchereria bancrofti, spread by Culex mosquitoes. The worms live in the lymphatic vessels and block them, so the legs or other body parts swell over a long time. It is a chronic condition and does not flare into outbreaks.
A is wrong: cholera, caused by the bacterium Vibrio cholerae through contaminated water, often spreads in epidemics.
B is wrong: malaria, caused by Plasmodium and spread by the female Anopheles mosquito, breaks out as epidemics after rains and floods.
C is wrong: smallpox, caused by the variola virus, swept the world in epidemics until it was eradicated in 1980.
Exam tip: endemic – always present in a region; epidemic – sudden outbreak in a community; pandemic – spread across countries or the world.
Practice Questions
View allSyngamy results in formation of
- A.haploid zygote
- B.diploid zygote
- C.non-motile male gametes
- D.motile male gametes
Show answer
Syngamy is the fusion of a male and a female gamete, and since each gamete is haploid, their union gives a diploid zygote.
Read the full explanation →Human insulin molecule is composed of one α-chain having 21 amino acids and one β-chain having 30 amino acids. How many functional insulin genes occur in adult humans?
- A.One
- B.Two
- C.Three
- D.Four
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Humans have a single functional insulin gene, INS, on the short arm of chromosome 11, and both chains of insulin come from it.
Read the full explanation →Which one of the following is the value of one nanometer?
- A.10⁻⁷ cm
- B.10⁻⁶ cm
- C.10⁻⁴ cm
- D.10⁻³ cm
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One nanometre is 10⁻⁹ metre, and since one metre is 100 (10²) centimetres, it equals 10⁻⁷ centimetre. The prefix nano means one billionth.
Read the full explanation →Which of the following is the general formula for saturated hydrocarbons?
- A.CₙH₂ₙ₊₂
- B.CₙH₂ₙ₋₂
- C.CₙH₂ₙ₊₁
- D.CₙH₂ₙ₋₁
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Saturated open-chain hydrocarbons are the alkanes, and every alkane fits the formula CₙH₂ₙ₊₂. In a saturated hydrocarbon every carbon atom is joined to others only by single bonds, so each carbon holds the largest possible number of hydrogen atoms.
Read the full explanation →The unit of the force constant k of a spring is
- A.N-m
- B.N/m
- C.N-m²
- D.N/m²
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The spring constant is force divided by extension, so its SI unit is newton per metre. Hooke's law says that, within the elastic limit, the restoring force of a spring is proportional to how far it is stretched or compressed: F = −kx.
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