.
——Chatting online has become_________popular means of communication.
——That’s true.It is especially popular with__________young.
A 不填； the B a ; the C不填；不填 D a ；不填
One theory, ________ suggested by Harvard University, is that humans began cooking their food, thereby releasing nutrients locked in the raw food and reducing the time needed to chew it.
| A．which | B．as |
| C．that | D．what |
________ is shown in the report, teenager problems are often connected with family life education.
| A．Which | B．As |
| C．It | D．What |
They told me they had just arrived at the last destination ________ you went to last year.
| A．where | B．that |
| C．when | D．which |
．Soon children in the camp had many new friends, ________ they shared food, stories, and projects.
| A．for which | B．with whom |
| C．of which | D．to whom |
________ is often the case with human beings, many animals sleep a lot when young, but sleep much less when they get older.
| A．Which | B．What |
| C．As | D．That |