Respiration is a

Given below are two statements.
Statement $I$ - During respiration the respiratory substrate directly unite with oxygen.
Statement $II$ - The primary process of respiration consists of removal of hydrogen from the respiratory substrate.
In the light of above statements,Select the correct option given below:

Respiration occurs in .........

The most important feature of respiration is that it .....

Give scientific reasons:
$(1)$ The actual process of respiration occurs in the protoplasm and mitochondria of the cell.
$(2)$ The rate of respiration is slow in plants.

Which one of the following statements is $INCORRECT$ regarding the exchange of gases in plants?