Pls help its really hard

Which is the layer underground where all empty spaces are filled with a combination of air and water ?

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.

Mary is conducting an experiment on how pollution affects plant growth. how can she ensure that her data are reliable?