Eg: Do you know if/whether he has seen the film?I’m sorry to hear that your father is ill.She says she is going to go to Beijing next week.He tells me that his sister came back yesterday.She didn’t know why the boy was late again. (过去一般)I didn't know if/whether he had seen the film.（过去完成）I wondered when she was going to America.（过去将来）注意：当主句是一般过去时，而从句表示的是客观真理，自然现象，科学原理，格言等，从句仍然要用一般现在时。例如：Eg: He said （that the earth moves round the sun. / that light travels much faster than sound.）
The teacher told us （seeing is believing.）
