After a second thought, Bill ________ a better idea of how to solve the problem.

Having walked in the desert for several days，we finally reached what was called oasis，________. 

We are looking forward to ________ you as soon as possible.

Some solid evidence proves that water really exists on Mars, but unfortunately, there is still no             of life.

Having lived in China for 8 years, Helen has a good ____________ of both English and Chinese.