______ it have been the failure to pick up directions from the ground control that caused the air crash?
| A．Must | B．Could | C．Would | D．Should |
From the school name on the package, we guessed that it might belong to a student of our school.
| A．to mark | B．marking | C．marked | D．having been marked |
studying abroad can be hard, it can broaden your understanding of the word.
| A．If | B．While | C．Because | D．Since |
The problem wasn’t hard. The little girl worked it out quickly.
| A．that | B．much | C．enough | D．a little |
Jane accidentally where she had hidden the birthday present for her mother.
| A．turned out | B．let out | C．came out | D．took out |
An earthquake happened in Haiti on Jan.12,2010, many countries in the world paid close attention to.
| A．where | B．when | C．which | D．what |