Since his retirement, Peter Smith, who was______a teacher, has written four novels.

【正确答案】 C

【答案解析】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。句意是：彼特-斯密斯以前是老师，在退休后他已经写了四本小说。根据句意可推出正确答案是C选项。