the class are doing a__research of the Changjiang river

the class are doing a__research of the Changjiang river
the class are doing a__research of the Changjiang river

the class are doing a__research of the Changjiang river
further
do a research是做研究的意思,这里加further表示更进一步的.
或者也可以用detailed, 意思是详细的
参考下吧,希望对你有所帮助.

necessary 必要的，重要的