13. --Hi, Lydia. Are you going to the concert on Friday? - -I’d like to. But there are so many problems ____.
---Jack,do you mind if I use our computer for a while? ---Not at all.___.
— I have got a headache. — No wonder. You___________in front of that computer too long.
The expert insisted that silkworms were first raised by a woman in___________is now Hebei Province.
My grandfather is as ___________as a young man and hates sitting around doing nothing all day.
— I am afraid the task is too difficult for me, sir. —___________, Linda. Just believe in yourself!