Although Math is very difficult, you can’t_____.

Every year a great number of foreign tourists pay a visit to _____ we Chinese call Heaven Lake.

continued to rise ______ pay was stilllow, with the result ______ the government became increasingly unpopular

It often happens that people with good eyesight fail to seeis right in front of them.

The idea they have come up with sounds great, but it remainswhether it works well in practice．