Answer:
A. distributing
Step-by-step explanation:
To give out in this context means to distribute - to give a share or a unit of something to each of a number of recipients. The unit in question here is a questionnaire each one of the participants received.
The rest of the meanings do not fit the context. Questionnaires are not donated (given for a good cause, like money to a charity), conferred (granted; given like a title, benefit, or right), or sacrificed (given up for the sake of something else).