天然气主要是由_________和__________元素组成的气态化合物，天然气的主要成分是____。沼气、瓦斯的主要成分也是____。
碳；氢；甲烷；甲烷
When he borrowed the camera last time, he broke it and I had to pay to get it ________.
A．repair
B．repairing
C．to repair
D．repaired
Though we spent a lot, we think it _____ because we succeeded in the end.
A．worth
B．worth being spent
C．worthy of
D．worthwhile
