help the plant to get moisture. anchor the plant in the ground. protect the plant from harm. support the stems and branches.
I gave my students this multiple choice question: The purpose of thorns on a plant is most likely to

Only one answer is correct among these 4 choices:
- help the plant to get moisture.
- anchor the plant in the ground.
- protect the plant from harm.
- support the stems and branches.

Could you tell me which one is correct?

protect the plant from harm.