Could宾语从句是一般过去时态或者一般现在时态。他的动词原形是can。例如，the boy could swim very well at the age of eight.这个男孩在八岁的时候游泳游的非常好。

Could you tell me why you are  strict with your students?你能告诉我，你为什么对你们班的学生那么严格吗