题目内容
（请给出正确答案）
[主观题]
The following machine is called ______. A. cable skidder B. grapple skidder. C. clam－bunk skidd
The following machine is called ______.
A. cable skidder
B. grapple skidder.
C. clam-bunk skidder.
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B、In vitro testing of biomaterials is done in the living tissue of a living organism.
C、The advantage of in vitro testing is that the experiment can be controlled easily and precisely.
D、In vivo tests include animal testing such as rat, pig, machin and clinical trials in humans.
