The reservoir pool of carbon is

The maximum evolution of oxygen is by which of the following producers of organic matter?

Some of the nutrient cycles are labelled as below:
$I$. Sulphur cycle
$II$. Phosphorus cycle
$III$. Carbon cycle
$IV$. Nitrogen cycle
Of these,the sedimentary cycle is represented by:

Herbivores are called

Identify the correct statements from the following:
$(1)$ Succession occurring in dry areas is called xerarch succession.
$(2)$ The stage where plants can survive in open conditions throughout the year is the herb stage.
$(3)$ Ecological succession leads to a decrease in the net primary productivity of the community.
$(4)$ Primary succession takes an average of $1000$ years to complete.

Assertion $(A):$ $A$ natural ecosystem is usually self-sustainable.
Reason $(R):$ An ecosystem having producers,decomposers,and a source of energy is self-sustainable. Select the correct answer from the options given below: