Energy enters into the ecosystem through

The flow of energy declines from lower to higher trophic levels in an ecosystem,which is mainly explained by:

Assertion $A$: Heat energy is available for the functioning of a system.
Reason $R$: Some amount of energy is lost during energy transformation.
Which option is correct for Assertion $A$ and Reason $R$?

Assertion : $A$ network of food chains existing together in an ecosystem is known as food web.
Reason : An animal like kite cannot be a part of a food web.

In an ecosystem, $1000 \ J$ of energy is stored at the producer level. How much energy will be available at the secondary consumer level (in $J$)?

In a terrestrial ecosystem, which type of food chain is the major conduit for energy flow?