Causation can be proved by using a (n):

A

negative correlation.

O

B. experiment.

O

c. observatior ...

D. hidden variable.

Answer : experiment!

I would say B

Explanation:

To prove Causation you need a random experiment. This could mean D because random experiments entail hidden variables but I think your best bet is B because its what's the use of a hidden variable without an experiment.