单选题 The boy dived into the water and after ______ seemed to be a long time, he came up again.
A. what B. that C. it D. which

【正确答案】 A
【答案解析】解析：本句意为：男孩纵身跳入水中，之后感觉过了很长一段时间，才又露出头来。after是连词，后面可连接一个句子，本句缺少主语，只有what能充当。