1. Children are always ______, and usually think differently from adults.
     A. satisfied    B. social    C. untrue      D. creative
2. When I was young, my father taught me that the earth ______ around the sun.
     A. moved     B. had moved
     C. was moving    D. moves
3. He mentioned in the letter that he ______ join us once he ______ our invitation.
     A. would come; received             B. had come; received
     C. was coming; had received      D. came; received
4. As consumers, we should be careful not to ______ the tricks of advertisers.
     A. care for    B. fall for
     C. ask for     D. answer for