(i) If both A and R are true: R is the correct explanation of A.
(ii) If both A and R are true but R is not the correct explanation of A.
(iii) If A is true but R is false.
(iv) If A is false but R is true.
Assertion (A): The rate of transpiration decreases in dry atmosphere.
Reason (R): In humid atmosphere, the rate of transpiration decreases.