Can someone answer? (Don't respond if you don't know)

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.

16. in a reaction that has reached equilibrium, a. the forward and reverse reactions are occurring at the same rate. b. the reactants and products are in equal concentrations. c. the forward reaction has gone further than the reverse reaction. d. there are equal numbers of atoms on both sides of the equation. e. a, b, and d are correct.

The identities of substances are the same before and after which type of change