Little Quack
New member
- Joined
- Nov 19, 2012
- Member Type
- Student or Learner
- Native Language
- Vietnamese
- Home Country
- Vietnam
- Current Location
- Vietnam
Hi everybody. 
When dealing with my exercise, I encountered one question.
May I ask you this now, please? 
The scientific evidence does not enable us to say with certainty that mobile phones are categorically safe. On the other hand, current research has not yet ______ clear adverse effects associated with the prolonged use of mobile phones.
A. demonstrated
B. produced
C. proved
D. caused.
The key is A but could you tell me why not C, please? Please help me out.
Any help would be greatly appreciated. 
When dealing with my exercise, I encountered one question.
The scientific evidence does not enable us to say with certainty that mobile phones are categorically safe. On the other hand, current research has not yet ______ clear adverse effects associated with the prolonged use of mobile phones.
A. demonstrated
B. produced
C. proved
D. caused.
The key is A but could you tell me why not C, please? Please help me out.