If you are very quiet, you can hear d music from the circus in town.
Each student is allowed to borrow two books at a time from the school l________.
About 71 percent of the earth’s surface is c________ by water.
The writer was _____(教育)at a very good school.
He is not_____ (身体上地 )ill but mentally (思想上地) ill.
_____(生物化学)is very popular in science today.