Tourism, _______ it brings in money to a country, can also result in damage to the World
Heritage sites there.
| A．once | B．while | C．if | D．as |
She pretended _______ me when I passed by.
| A．not to see | B．not seeing | C．to not see | D．having not seen |
There’re so many kinds of tape-recorders on sale that I can’t make up my mind _____ to buy.
| A．what | B．which | C．how | D．where |
—How’s your tour around the North Lake? Is it beautiful?
—It ________ be, but it is now heavily polluted.
| A．will | B．would | C．should | D．must |
John promised his doctor he _____ not smoke and he has never smoked ever since.
| A．might | B．should | C．could | D．would |
According to the air traffic rules, you ___ switch off your mobile phone before boarding.
| A．may | B．can | C．would | D．should |