When forbidden to surf the Internet, teenagers often __________ it, saying that it provides them with colorful entertainments, a convenient means of communication as well as useful information.
Our classroom is very clean. Do you know who___cleaned it?
—— Was that the new comer who walked by? —— _____.
____being March 12th, they planted trees on the hill.
—— Have you ever seen a whale alive? —— Yes, I’ve seen ___.
____four years since I joined the army.