Which of the following are known as the 'pioneer species' in primary succession?

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.

Match the following:

Trophic levels	Examples
$A$. First	$a$. Man
$B$. Second	$b$. Wolf
$C$. Third	$c$. Cow
$D$. Fourth	$d$. Phytoplankton

Identify the stage of hydrarch succession shown in the figure.

Amount of inorganic substances present in an ecosystem is . . . . . . Energy flow is a . . . . . . feature of ecosystem.

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