Until the start of the Industrial Revolution, mankind was poor, hungry, and constantly at the _______ of disease and natural disasters.

—Do you know why Jane was so angry?—Her roommate gave in to ________ and opened the letter addressed to her.

Listening to music is a good way to help us get some ______ from work pressure.

The government decided to tear down the old bridge, which was not strong enough to allow the ___ of heavy vehicles (车辆).

 Invention can be ________ as it may suddenly begin just by noticing something usual.