Although the causes of cancer ________, we do not yet have any practical way to prevent it．
| A．have uncovered | B．have been uncovering |
| C．are uncovering | D．are being uncovered |
______ is a best-known secret in success that get ready in much of our life and you may make the most of the opportunity．
| A．What | B．As | C．It | D．That |
As many successful businessmen believe, courage is as ______ to pioneering work as the intelligence, even more so．
| A．accessible | B．essential | C．alternative | D．commercial |
— Oh, really? Can Doris read through it in such a short time?
— She covered the English novel ______ it took me, still less a simple story．
| A．a half time | B．the half time | C．half a time | D．half the time |
In case you ______ still have anything to offer, please contact our manager while he is available．
| A．shall | B．would | C．should | D．will |
Malaysia Airlines Flight MH370 seemed to have been ______ to only a mystery after so long and hopeless a search．
| A．reduced | B．formed | C．trapped | D．absorbed |