--- Why does the lake smell terrible?
--- Because large quantities of water _________.
| A．have polluted | B．is being polluted |
| C．has been polluted | D．have been polluted |
27．These natural parks aye very important for preserving animals，which would_______-run the
risk of extinction．
| A．otherwise | B．therefore | C．besides | D．However |
26．— I’m sorry．I’ve left my wallet home．So I don’t have enough cash for the meal．
— Take it easy．_____
| A．It’s a piece of cake． | B．It’s my pleasure to pay you． |
| C．It’s my treat． | D．It’s at your expense． |
25．Putting the worries out of her mind，Mary turned her efforts__________the evening meal．
| A．toward | B．beyond | C．off | D．Inside |
24．This is an exciting area of study，_______new applications are being discovered almost daily．
| A．one by which | B．the one where | C．one in which | D．the one by which |
23．— What’s that terrible noise．David?
— Oh，I forgot to tell you．The new machines in the nearby plant _______．
| A．were tested | B．will be tested | C．are being tested | D．have been tested |