I really need an answer please help

Write the symbol for every chemical element that has atomic number greater than 3 and atomic mass less than 12.0 u.

This chart lists four kinds of polymers and their sources. what can be known about all four polymers, despite their differences? they come from living things. they share ionic carbon bonds. they are at least 100 monomers long. they are made of repeating subunits.

In which reaction is precipitation occurring?