Which of the Following Is an Experimental,as Opposed to a Correlational,type

Which of the following is an experimental,as opposed to a correlational,type of study?

A) Pictures of same-sex or heterosexual sexual activities are shown to two groups of randomly sampled participants.Later,participants in both groups are asked questions such as,"Do you ever think about same-sex activities?" The responses are compared between the groups.
B) Pictures of same-sex and heterosexual sexual activities are shown to randomly sampled gay and heterosexual participants.Later,participants are asked to rate their enjoyment of the pictures.The responses are compared between the groups.
C) Sexual desire is compared between pre- and post-menopausal women.
D) In a laboratory setting,vaginal lubrication is compared between women who have had more than three sexual partners and those who have had no sexual partners.