原虫的构成是
A. 细胞膜
B. 细胞质
C. 细胞核
D. 核仁
Where did the fish choose to stay in the unique dish tank?
A. They preferred to stay in the clean section.
B. They preferred to stay in the empty section.
C. They preferred to stay in the natural section.
D. They preferred to stay in the unnatural section.
What did the researchers do after they gave the fish shots?
A. They gave all the fish in the fish tank some painkilling shots.
B. They put painkilling medicine in the water of both sides of the fish tank.
C. They put painkilling medicine in the water of the natural side of the fish tank.
D. They put painkilling medicine in the water of the empty side of the fish tank.
What happened after the researchers put painkilling medicine in the water?
A. Fish that received the painful shot stayed in the natural section.
B. Fish that received the painful shot moved into the empty section.
C. All of the fish stayed in the natural section with plants and rocks.
D. All of the fish moved into the empty section with painkilling medicine.
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