Assertion (A) : The amount of ozone in the atmosphere began to drop sharply in the 1980s.

Reason (R) : The oxygen atoms combine with molecular oxygen to form ozone.

options

1. (A) and (R) are true and (R) is the reason for (A).
2. (A) and (R) are true and (R) is not the reason for (A).
3. (A) is true, but (R) is false.
4. (A) is false, but (R) is true.

A student performs the following experiment in his school laboratory.

List two observations to justify that in this experiment a chemical change has taken place.

Besides minimising the loss of blood, why is it essential to plug any leak in a blood vessel? Name the component of blood which helps in this process and state how this component perform this function.

(a) The transport system in plants is relatively slower than in animals. Give reasons.

(b) State the role of phloem in the transport of materials in plants.