We        the problem for a long time, but we didn’t reach any agreement.

Air and the sun's rays create much distortion, and whatever tends to _____ their influence is useful to the astronomer.

Heating the news that my father was ill，I was so worried that I couldn’t        on anything．

   Tom received an invitation from Carrol but he ______.

___ staying at hotels in Red River Village, tourists can help the villagers make money so that they can take _____the river and the birds.