Which of the following sentences is CORRECT？A．What do you say that the population of Beiji

Which of the following sentences is CORRECT？

A．What do you say that the population of Beijing is？

B．How many people do you think to stay here？

C．Who do you guess is singing？

D．What do you tell that is？

请帮忙给出正确答案和分析，谢谢！