Why negative and positive signs can be useful additions to displacement values

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

The following hormone had their receptors in the cell membrane except a-insulin b-tsh c-gh d- cortisol

Graphs you see question 5 options: the change in data over time the relationship between different dependent variables the relationship between the independent variable and the dependent variable/s the relationship between different independent variables