期货套利交易者是指单向头寸拥有者。 ( )
参考答案：错
—I ______ something wrong just now. May 1 use your eraser?
—Of course. Here you are.
A. write B. wrote C. am writing
How did you manage to get to school on time ______ you missed the school bus?
A．when
B．if
C．once
D．because
