In order to protect the environment，people are greatly encouraged to travel by public________.
| A．transport | B．service |
| C．means | D．transfer |
Raising environmental awareness was the aim of our art exhibition ____ last week.
| A．to hold | B．held | C．having held | D．being held |
_________ he was, he still went on with his work.
| A．Tired although | B．Tiring as | C．Tired though | D．While tired |
It is ten years since we ________ each other last time．
| A．see | B．have seen | C．saw | D．had seen |
More wild tigers have been seen in the forest around this area, ________ there used to be very few.
| A．when | B．where | C．what | D．which |
It is usually warm in my hometown in March, but it ________ be rather cold sometimes.
| A．must | B．can | C．should | D．would |