He smiled politely ________Mary apologized for her drunken friends. [ ]

Do you know the mission of the volunteers?—NoBut I think _____ they will end up doing there will promote public awareness of environmental protection

_____ call him if you want to, but you _______,for he’ll surely come here soon

the fruit-pickers, several of _______were still university students.

(2013·河北石家庄二模)—________ has brought worldwide attention to China?—Rapid and steady economic growth, of course.