单项选择题
Don't disturb me. I（）letters all morning and have written ten so far.
A.write B.have written C.was writing D.have been writing
单项选择题 I’ve come to ask him for the book. That’s why I （） wait until he comes back.
单项选择题 Mr. Baker, a dozen students want to see you. （） they wait here or outside?
单项选择题 I （） help. I can do it myself.
