Which one of the following living organisms gives litmus ?
- A.Protozoa
- B.Virus
- C.Lichen
- D.Saccharomyces
Correct answer
Explanation
The correct answer is C, Lichen. Litmus is a natural dye extracted from certain lichens, especially species of Roccella.
A lichen is a partnership between a fungus and an alga (or a cyanobacterium): the alga makes food by photosynthesis, while the fungus gives shelter and absorbs water and minerals. The dye obtained from lichens is purple in neutral solution. Acids turn blue litmus red and bases turn red litmus blue, which makes it one of the oldest acid-base indicators. Lichens are also sensitive to sulphur dioxide, so they serve as indicators of air pollution.
A is wrong: protozoa are single-celled animal-like organisms such as Amoeba and Plasmodium; they do not yield litmus.
B is wrong: viruses are not cells and produce no dyes; they multiply only inside living host cells.
D is wrong: Saccharomyces is yeast, a fungus used for fermentation in baking and brewing, not a source of litmus.
Exam tip: litmus comes from lichen (fungus + alga), a natural acid-base indicator; lichens also signal SO₂ pollution.
Practice Questions
View allWhich one of the following cell organelles contains DNA?
- A.Golgi apparatus
- B.Mitochondrion
- C.Lysosome
- D.Endoplasmic reticulum
Show answer
Mitochondria carry their own small, circular DNA and their own ribosomes. Mitochondria are the powerhouses of the cell, where aerobic respiration makes ATP.
Read the full explanation →Which set of vegetables is underground stem or modified stem of a plant?
- A.Potato, artichoke, round gourd
- B.Onion, garlic, carrot
- C.Potato, onion, garlic
- D.Potato, garlic, turnip
Show answer
All three are underground modified stems: the potato is a stem tuber, and onion and garlic are bulbs. A stem can be told from a root by its nodes and buds.
Read the full explanation →A sound wave having frequency of 300 Hz is travelling in an unknown medium. Its wavelength is not known. It travels a distance equal to 150 times its wavelength in time t. The value of t is :
- A.0.5 s
- B.1 s
- C.1.5 s
- D.2 s
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A wave moves forward by one wavelength in each cycle, so 150 wavelengths take 150 cycles, and 150 cycles at 300 per second take half a second.
Read the full explanation →A body floats in a liquid if the buoyant force is :
- A.equal to its weight.
- B.less than its weight.
- C.greater than its weight.
- D.zero.
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A floating body is in equilibrium, so the upward buoyant force exactly balances its weight. By Archimedes' principle, a body in a liquid is pushed up by a force equal to the weight of the liquid it displaces.
Read the full explanation →Which of the following are the different parts of a human brain ?
- A.Forefront brain, Standard brain and Hind brain
- B.Fore brain, Median brain and Rear brain
- C.Fore brain, Mid brain and Hind brain
- D.Precursor brain, Mean brain and Hind brain
Show answer
These are the three main divisions of the human brain. The fore brain is the largest part.
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