______ it have been the failure to pick up directions from the ground control that caused the air crash?
At the end of the meeting, it was announced that an agreement ________.
----She looks happy. She _______ have passed the exam. -----I guess so. It is not difficult after all.
Choosing the right dictionary depends on ______ you want to use it for.
More than a dozen students in that school _______ abroad to study medicine last year.
----Why did you leave that position? ----I ______ a better position at IBM.