问题
选择题
After Jack had sent some e-mails, he _______ working on his project.
A．had started
B．has started
C．started
D．starts
答案
答案：C
考查动词时态。根据前半句的谓语动词用了过去完成时，可知后半句用一般过去时，这样才能符合“过去的过去”这一条件。句意：Jack发了几份电子邮件之后，他才开始研究他的项目。