Past Perfect Continuous — Bài Tập 5

I wondered what they ______ because they were laughing so much.

We ______ about you just before you called.

The scientist ______ the experiment for months with no results.

How long ______ before you realized your mistake?

I could tell she ______ because of the smell of fresh paint.

For months, the child ______ that a monster lived under his bed until his parents showed him there was nothing there.

We ______ the problem from the wrong angle until you explained it.

The patient ______ signs of improvement for weeks, which gave the doctors hope.

I ______ a strange dream when the alarm clock woke me up.

Her eyes were tired because she ______ on the computer all day.