There are many valuable services which the public are willing to pay ___, but which __ not bring a return in money to the community.
| A．to; do | B．不填；does | C．for; does | D．for; do |
I remembered _____ the door before I left the office, but forgot to turn off the lights.
| A．locking | B．to lock | C．having locked | D．to have locked |
Teachers required that all the students ___ their homework all alone.
| A．must finish | B． would finish | C．had to finish | D．finish |
His favorite food is fried snack and soft drinks. ______ is no surprise that losing weight is just his dream.
| A．There | B．It | C．As | D．What |
The most interesting thing to the small boy was _______ he got close to the door, it would open of itself.
| A．that as | B．that that | C．what that | D．what when |
Please keep______ secret that he' s decided to give up his present position.
| A．one | B．it | C．this | D．that |