Our teacher is always busy preparing lessons until 11 o’clock at night, _______we students have gone to sleep.
The wet weather will continue tomorrow, when a cold front ______ to arrive.
His sister left home in 1998, and _______since.
When I talked with my grandma on the phone, she sounded weak, but by the time we ___ up, her voice had been full of life.
The way the guests ___ in the hotel influenced their evaluation of the service.
Scientists have many theories about how the universe ___ into being.