Which trend in hominid evolution can be supported by fossil evidence?
Walking upright
Use of tools
Increased intelligence
Decorating cave walls

Walking upright.

You can make a case for all of them, but for three of them indirectly.

But the answer, I think, is walking upright.

You can look at the pelvic bones and femur orientation in the hips. You can also look at the way the skull sits on the vertebra.

Chimpanzees have a skull that sits more downward, because they walk on all fours most of the time. While humans have skulls that sit more horizontally on the vertebra, which allows us to see out on the horizon more easily. We can do that because we stand on two feet.

I hope that helps.