The first use of atomic weapons was in 1945, and their power increased enormously ever since.
| A．is |
| B．was |
| C．has been |
| D．had been |
An engineer has designed _______ robot that can work in _______ deep sea to clean waste.
| A．a; the | B．a; a | C．/; the | D．the; / |
—What do you think I should wear for such a formal press conference?
—Dress _______ you like.
| A．how | B．what | C．whatever | D．however |
Radium salts，which have been found to ______ in bones，give rise to bone cancer.
| A．pile up | B．build up | C．keep up | D．pull up |
Our teacher insisted that the key words worth paying attention _______ before class.
| A．be underlined | B．being underlined |
| C．to be underlined | D．to being underlined |
With some technical problems to be solved, it may be a while _______ the system is put into use.
| A．when | B．after | C．since | D．before |