In the following studies, state whether you would use a one-sample t test or a two-independent-sample t

Question:

In the following studies, state whether you would use a one-sample t test or a two-independent-sample t test.
(a) A study measuring differences in attitudes about morality among Democrats and Republicans
(b) A study testing whether night-shift workers sleep the recommended 8 hours per day
(c) An experiment measuring differences in brain activity among rats placed on either a continuous or an intermittent reward schedule