共生固氮菌(symbiotic nitrogen-fixer)
Language change is ______.
A.universal, continuous and to a large extent, regular and systematic.
B.continuous, regular, systematic, but not universal.
C.universal, continuous, but not regular and systematic.
D.always regular and systematic, but not universal and continuous.
The bacteria depend on worms for hydrogen sulfide in the symbiotic relationship.
A.Y
B.N
C.NG
The most______(convince)evidence of black holes comes from research into binary star systems.
A.Chemosynthetic.
B.Heterotrophic
C.Photosynthethic
D.Symbiotic
These mine planets ,together with the sun ,make up what _______(call) our solar system.
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