单选题
From the passage we know that joints and muscles perform best when______.
A、
they are twisted and stretched
B、
they are in their normal position
C、
they are tested with a human" guinea pig"
D、
they are tested with electronic instruments
【正确答案】
B
【答案解析】
[分析] 见第一段的第四句。
提交答案
关闭