______ we had read your letter ______ the true state of affairs.
| A．It was until; that we understood |
| B．It was not until; that we understood |
| C．Until; did not we understand |
| D．Not until; we understand |
________ this cake, you'll need 2 eggs, 175 g sugar and 175 g flour．
| A．Having made | B．Make | C．To make | D．Making |
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 |
Someone who lacks staying power and perseverance is unlikely to _________ a good researcher．
| A．make | B．turn | C．get | D．grow |
They _________ two free tickets to Canada, otherwise they'd never have been able to afford to go．
| A．had got | B．got | C．have got | D．get |
—Have you been wasting time on computer games again?
—________．I've been studying a lot and I need a break．
| A．No way | B．Not really | C．I don't agree | D．I couldn't agree more |