Analysis of the stone artifacts from zhoukoudian indicate that the tools from:
the later stages are heavier and larger than the previous stage.
all stages are identical to each other.
the earliest stages are made from flint and fine-grained quartz.
the later stages are small and the tool materials are of better quality than the previous stages.
the later stages are large and crudely made.

the later stages are small and the tool materials are of better quality than the previous stages.

Explanation:

The stone scrapers and the choppers found at the site of Zhoukoudian points out the fact that Peking men devised several tools for various purposes and to accomplish different tasks. The stones and the bones used to make the tools used to be charred by using the fire. This also indicates that the Peking men had discovered the uses of fire and they used fire for various activities.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

the correct answer is b