The word translated as "members" refers to parts of a body. Our belonging to Christ is spoken of as if we were parts of his body. We belong to him so much that even our bodies belong to him. Paul uses this question to remind the people of something they should already know. Alternate translation: "You should know that your bodies belong to Christ" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-rquestion]])
Paul uses this question to emphasize how wrong it is for someone who belongs to Christ to go to a prostitute. Alternate translation: "I am part of Christ. I will not take my body and join myself to a prostitute!" or "We are parts of Christ's body. We must not take our bodies and join ourselves to prostitutes!" (See: [[rc://en/ta/man/translate/figs-rquestion]])