_____ we continue to kill elephants for their ivory，we humans will lose them in the end．（ ）
| A． |
If |
B． |
Before |
C． |
Until |
D． |
Although |
In the past 70 years， China______historic changes and made great achievements．（ ）
A．experiencedB．has experienced
C．experiencesD．would experience
Is Helen here？
Not yet， but she_________in half an hour．（ ）
A．arrivesB．will arrive
C．arrivedD．has arrived
Do you think teenagers can't have a part﹣time job？
_____________．They may learn from working．（ ）
A．It's nothingB．Don't mention it
C．Hard to sayD．That's all right
I hear you've got an "A" in your English test． Congratulations!
____________．（ ）
A．It's a pleasureB．Take it easy
C．Many thanksD．You' re welcome
Sorry to interrupt you and Frank!
_________．We' re having a free talk．（ ）
A．Never mindB．Go ahead
C．I hope notD．That would be nice