Tom’s mother often requires that he more time in studying English every day.
The bell rang and came in Mr.Brown, a book in his hand. Then the class began.
In the past 5 years a great deal of money _____ improving the environment of the school.
China has been working very hard to stop the endangered animals ______ .
I ______their method of making the machine .
The blues has been _____part of African-American culture since then, and it is still ______ important part of American culture.