When you visit a museum you must ask for _____ before taking photographs inside it. 

In manufacturing, cheaper materials are constantly being        for the better, more expensive kind.

(2013·南京二模)—What do you think of the news in today's newspaper?—We shouldn't ________ the trouble of helping others only because what we do may invite trouble.

We often see the situation of employers_____________ people they want, while job seekers can't find the employers they want.

(2013·江西十所重点中学高三二模)Many people headed for the water to ________， including rivers, bays in the seaside of the country.