CBSE Class 7 Science Advanced Biology Food and Food Preservation MCQs Set 01

Answer: (d) adding sugar

Explanation:
1. Sugar draws water out of the food, so microbes cannot grow in it.
2. Fruit jams and fruit preserves are traditionally kept by adding a large amount of sugar.
3. Smoking, heating and oiling are used for other foods, so the answer is (d) adding sugar.

Teacher's Note:
1. Link each method to a food: sugar with jams, oil and salt with pickles.
2. Sugar works by holding on to water that microbes need.

Answer: (d) Vitamin D – Goitre

Explanation:
1. Vitamin A deficiency gives night blindness, vitamin C deficiency gives scurvy and vitamin B deficiency gives beriberi, so (a), (b) and (c) are right.
2. Goitre is caused by lack of iodine, and vitamin D deficiency causes rickets.
3. So the wrong match is (d) Vitamin D – Goitre.

Teacher's Note:
1. When asked for the wrong match, check each pair one by one.
2. Goitre always goes with iodine.

Answer: (d) weak bones

Explanation:
1. Calcium is the mineral that builds bones and teeth.
2. Without enough calcium the bones become weak and teeth decay.
3. Rickets is linked in this chapter with vitamin D, anaemia with iron and goitre with iodine. The answer is (d) weak bones.

Teacher's Note:
1. Follow the chapter's table: each nutrient has its own disease.
2. Calcium means bones and teeth.

Answer: (b) scurvy

Explanation:
1. Bleeding gums are the sign of the vitamin C deficiency disease.
2. That disease is scurvy, so the answer is (b) scurvy.
3. Anaemia gives weakness, goitre gives a swollen neck and beriberi gives weak muscles.

Teacher's Note:
1. Remember: Vitamin C, scurvy, bleeding gums.
2. Citrus fruits and amla supply vitamin C.

Answer: (a) rickets

Explanation:
1. Vitamin D helps the body use calcium to harden bones.
2. When it is lacking in a child, the bones stay soft and bend, a disease called rickets.
3. So the answer is (a) rickets.

Teacher's Note:
1. Bent legs in a child usually suggest rickets.
2. Sunlight and milk help the body to get vitamin D.

Answer: (b) A–(iii), B–(iv), C–(ii), D–(i)

Explanation:
1. Night blindness is due to vitamin A deficiency, so A matches (iii).
2. Goitre is due to iodine deficiency, so B matches (iv).
3. Anaemia is due to iron deficiency, so C matches (ii).
4. Rickets is due to vitamin D deficiency, so D matches (i).
5. The combination A–(iii), B–(iv), C–(ii), D–(i) is option (b).

Teacher's Note:
1. Match the easy pairs first and cross out options.
2. Eliminate options that pair even one disease with the wrong cause.

Answer: (b) Heating the milk at 72°C for 15 seconds

Explanation:
1. In pasteurization the milk is heated for a short time and then cooled suddenly.
2. The standard condition given in the chapter is 72°C for 15 seconds.
3. So the answer is (b).

Teacher's Note:
1. Learn the numbers 72°C and 15 seconds.
2. It is heating then quick cooling, not just chilling.

Answer: (c) A is true, but R is false.

Explanation:
1. Salt pulls water out of microbes and food, so microbes cannot grow. Hence the Assertion is true.
2. The Reason says that salt increases the moisture, which is false, because salt removes moisture.
3. So A is true and R is false: option (c).

Teacher's Note:
1. Salt works by dehydration, not by adding water.
2. Read the reason carefully, one wrong word can make it false.