Don't scold him; even an experienced engineer _____ make such a mistake after all.
| A．must | B．can | C．should | D．dare |
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 |
He gave me the phone number in order ______ contact him when we are in need of help.
| A．to | B．of me to | C．for me to | D．that I |
You know that widely reading helps ______ your knowledge so I can’t help _____ the housework every day.
| A．an large, doing | B．to rich, to do | C．add, to | D．add to, doing |