More bison were killed.The bison population is thought ______ from 60 million to just a few hundred between 1850 and 1910.
In the past, ice used to ______ used to ______ the air in a room.
The old man’s _______ pity on the snake led to his own death.
________ many times, but he still could not understand it.
Faced with a bill for $ 10,000,_________.
-----My room gets very cold at night. -----_________________.