联合固氮作用 associative nitrogen fixation
参考答案:
自生固氮微生物在高等植物影响下促进的固氮作用。
The small mountain village we spent our holiday last month lies in is now part of Hubei .
A.which where
B.where, what
C.that , which
D.when , which
期货交易的形式有( )。
A.实物期货
B.货币期货
C.利率期货
D.汇率期货
E.股票指数期货