For the Assertion (A) and Reason (R) below, choose the correct alternative.
Assertion (A) : Bats can fly in the night.
Reason (R) : Bats emit ultrasonics.
Answer: A
Bats can fly in the night because they can trace the obstacle in the path by perceiving the echo of the ultrasonic sound emitted by them after it is reflected by the obstacle.
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Assertion (A) : Carbon dioxide turns lime water milky.
Reason (R) : Carbon dioxide sullies the water.
Answer: C
Carbon dioxide reacts with lime water (calcium hydroxide) to form milky precipitate of calcium carbonate
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Assertion (A) : a Vaccines prevent diseases.
Reason (R) : Vaccines must be given to children.
Answer: B
Vaccines prevent diseases by developing immunity inside the body and vaccines must be given to children to build in them a resistance against diseases.
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Assertion (A) : An atom is neutral despite the charged particles in it.
Reason (R) : The neutrons do not have any charge.
Answer: B
An atom contains the positively charged protons and an equal number of negatively charged electrons So, it is neutral
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Assertion (A) : Leakages in household gas cylinders can be detected.
Reason (R) : LPG has a strong smell.
Answer: C
Leakages in household gas cylinders can be detected because of the strong smell of ethyl merceptan mixed with LPG.
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Assertion (A) : Inside the earth metals are present in molten state.
Reason (R) : Earth absorbs the sun's rays.
Answer: C
Inside the earth, the high temperature and pressure keeps the metals in molten state. The earth does not absorb the sun's rays but reflects them
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Assertion (A) : Red colour of blood is due to haemoglobin.
Reason (R) : Haemoglobin is a red pigment.
Answer: A
Haemoglobin is the blood pigment that imparts red colour to the blood.
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Assertion (A) : Clothes are not washed properly in hard water.
Reason (A) : Hard water contains many minerals.
Answer: B
Clothes are not washed properly in hard water because it does not form lather with soap. However, it is true that hard water contains many minerals.
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Assertion(A) : The steam engine was invented by James Watt.
Reason(R) : There was a problem of taking out water from flooded mines.
Answer: A
The problem of pumping out water from the flooded mines provided the need of self-working engine, which led James Watt to invent the same.
Thus, both A and R are true & R correctly explains A.
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Assertion(A) : The pouring of kerosene oil on stagnant pools helps to eradicate malaria.
Reason(R) : The kerosene oil is poisonous for the mosquitoes.
Answer: C
The kerosene oil sprayed on the water provodes a thin cating and the larvae of the mosquitoes are prevented from coming up to breathe. Thus, they die.
Hence, A is true but R is false.
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