答案：C

题目分析：句意：这是我第一次享用这种月饼。在“It is/was/will be the first time that分句”结构中，当主句动词为is/will be时，that分句动词一律用现在完成形式，引导词that可以省略。如：It is the first time I‘ve been here.我第一次来这里。又如Don’t forget，it’ll be the first time I‘ve spoken in public；别忘了，这是我第一次在公开场合讲话。当主句动词为was时，that分句动词通常用过去完成形式。It was the first time she’d been at a summer school and she thoroughly enjoyed it.那是她第一次参加夏令营，她很享受这次活动。