A scientist should be willing to change his theory if the evidence does not support it.

a. True

b. False

It is absolutely true that a scientist should be willing to change his theory if the evidence does not support it. The correct option among all the options given in the question is option "a". The scientist has to back up his theory with evidence, otherwise the theory is considered as false. to arrive at a successful conclusion, a scientist must be willing to change his theory when required.