单选题 Since his retirement, Peter Smith, who was ______ a teacher, has written four novels.
A. lately B. usually C. formerly D. already

【正确答案】 C

【答案解析】[解析] 句意是：彼得·史密斯以前是老师，在退休后已经写了四本小说。四个选项的意思分别是：lately“近来，最近”；usually“通常，大抵”；formerly“从前，以前”；already“早已，已经”。根据句意可推断出正确答案是C选项。