Who should be responsible for the accident?—The boss, not the workers. They just carry the orders _______.

Linda ______ the space museum after school yesterday.

It was at the airport _____ was completed last year _____ he worked as a volunteer helping foreigners in need of translation service.

What really worries us is ______ the explorers can accurately locate themselves with the device in case of bad weather.

When _______ different cultures, we often pay attention only to the differences without noticing the many similarities.