1. Unless someone **puts** the cold in, the fire will go out.
2. What about **helping** the street children?
3. Gustave Eiffel **designed** the Eiffel Tower in 1889.
4. Give old clothes to charity instead of **throwing** them away.
5. We learn how **to use** a computer in our computer science class.
6. The man **walking** upstairs is Mr. Quang.
7. Two hours **are** not enough to finish this task.