–Do you have any idea what your former boss would say about you? –I don’t know, ________.
It ________ some time _________ I realized the truth.
The annual Energy & Environment Conference calls on our human beings to _______environmental issues.
--- We need someone to host the New Year Party. --- ________ the handsome young man have a go?
Being a teacher always encouraging students to think for themselves, I won't tell them answers until they __________ on a math problem for more than an hour.
He could speak English fluently because he __________ it for four years when he was a college student.