I ONLY need help with C. I cannot come up with an answer. Not enough information for me to solve. Thank you. A teacher wishes to know whether the males in his/her class have more conservative...

I ONLY need help with C. I cannot come up with an answer. Not enough information for me to solve. Thank you.

A teacher wishes to know whether the males in his/her class have more conservative attitudes than the females. A questionnaire is distributed assessing attitudes.

a. Is this a sampling or a census?

b. Is this an observational study or an experiment?

c. Are there any possible sources of bias in this study?