Select all that apply.

which of the following are vertebrates?

starfish

earthworms

tunicates

crab

amphibians

lancelets

octopus

grasshopper

First, let's define vertebrate. 
Technically speaking, a vertebrate is in the sub-phylum Vertebrata (Phylum Chordata). It must have a notochord and/or spine.

Now we know what a vertebrate it, we can answer our question.

Are starfish vertebrates? No.
Are earthworms vertebrates? No.
Are tunicates vertebrates? No.
Are crabs vertebrates? No.
Are amphibians vertebrates? Yes.
Are lancelets vertebrates? Yes.
Are octopus vertebrates? No.
Are grasshoppers vertebrates? No.

Why? Grasshoppers and crabs have exoskeletons (No bones). Octopus and starfish have no spinal column/backbone. Does it look like Tunicates or earthworms have spines?

C. gemstones they are the only non metallic mineral from the list.