Generally speaking, ______according to the directions, the drug has no side effect.
| A．when taking | B．when taken | C．when to take | D．when to be taken |
Police in America have stepped up their search for a fifteen-year-old boy who went _____ three days ago.
| A．going | B．losing |
| C．missing | D．disappearing |
There are _____ flights between the two cities, _____ it convenient for people in one city to travel to work in the other.
| A．regular; to make | B．usual; making |
| C．usual; having made | D．regular, making |
Though faced with so many difficulties, they are _____ about their future.
| A．curious | B．enthusiastic |
| C．optimistic | D．concerned |
The Sahara Desert is almost _____ of the US.
| A．as big | B．the size |
| C．the area | D．the same |
---It’s a long time since I saw Marry.
--- _________ her this afternoon?
| A．Why not to | B．Why not visit her |
| C．Why not visiting | D．Why don’t visit |