I’m sorry I didn’t phone you,but I’ve been very busy ________ the past couple of weeks.
Hardly ___________the door when he rushed into the office out of breath.
The driver was at ___ loss when ____ word came that he was forbidden to drive for speeding.
We want such materials ________ can bear high temperature and pressure.
Her sister has become a lawyer, _____she wanted to be.
Space exploration has been made ______ with the development of modern science and technology.