1£®Scientists say it may be five or six years ________ it is possible to test this medicine on human patients.

2£®The task is very difficult.I wonder ________ we will be able to finish it in the absence of any other helpers.

3. ________  time went by£¬I came to realize that my parents could not always stand by me.

4. ________ fast is the city developing that you can never imagine what will be like tomorrow.

5£®Can you ________ (simple)the language a little£¿It's difficult to understand.

6£®Finding information in today's¡¡world is easy.The challenge is ________  you can tell if the information is useful or not.