New words：

troublesome ['trʌblsəm] adj.令人烦恼的；讨厌的；令人痛苦的；困难的；棘手的

Sample Sentences：

This naughty boy is really troublesome.
He needed surgery to cure a troublesome back injury.
The traffic jam has become a very troublesome issue of human life.

issue ['iʃju:] n. 问题；争论点；发布

New words：

gnaw [nɔ:] v. 啃；咬；啮；侵蚀

Sample Sentences：

The dog was gnawing a bone.
She was gnawing her nails nervously.
Some of the furniture in this old house has been gnawed away by rats.

New words：

get along with 相处；与…和睦相处；进展

Sample Sentences：

It's impossible to get along with him .
How are you getting along with your classmates?
He's such a strange person that we all find it hard to get along with him .

New words：

gill [gil] n. 鳃

Sample Sentences：

A fish breathes through its gills.
Fish take in oxygen through their gills.
Some animals, such as the Mexican salamander, have their gills on the outside.

New words：

tadpole ['tædpəul] n.蝌蚪

Sample Sentences：

Both fish and tadpoles have gills.
Now it is no more a tadpole; it has become a young frog.
Each tadpole has a mouth with tiny teeth to gnaw the plants.

gill [gil] n. 鳃
gnaw [nɔ:] v. 啃；咬；啮；侵蚀