2. The mammalian support system is an
with an branches

osteocytes, nerves

Explanation:

The mammalian support system includes many of the osteocytes which are trapped within the bone matrix. The osteocytes maintain a connection through tiny channels also called canaliculi. Through these channels, the nerves pass through in the form of branches supplying water, and nutrients to the bone. This entire system is supportive of mammalian structure.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation:

some fungi obtain their nutrients from a living host (plant or animal) and are called most biotrophic fungi have fairly narrow host ranges—they are specialized on a limited called rhizomorphs that allow the fungus to grow from one tree to another. ascospores are formed inside a sac-like structure called an ascus. so your answer is a