While Mikey was at the zoo, he classified the animals as he walked by their exhibits. Category 1 is for vertebrates, which are animals with a backbone. Category 2 is for invertebrates, which are animals without a backbone. The table Mikey made is shown below.

Category 1 Category 2
cat snail
mouse jellyfish
dolphin sponge

The last animal that Mikey needs to categorize is a earthworm. Into which category does it belong?
A.
neither category
B.
category 2
C.
both categories
D.
category 1