一Did you notice a strange man just now?
一Sorry，I ______of something else．
| A．thought | B．was thinking |
| C．have thought | D．had thought |
-----When will they come back?
-----I _____ don’t know.
| A．simply | B．hopefully | C．happen | D．as well |
She was more headstrong than ______.
| A．the rest of us | B．us the rest |
| C．the other of us | D．us the other |
Though ______, many laws of nature exist.
| A．not having been discovered | B．having not been discovered |
| C．not having discovered | D．having not discovered |
The servant did _____ she could ______ the revolutionary.
| A．what, help | B．that, to help | C．what, to help | D．all help |
The missing boys were last seen _____ near the river.
| A．playing | B．to be playing | C．play | D．to play |