问题
选择题
She ______ the national table tennis team in 1988. [ ]
A. joined in
B. joined
C. took part in
D. took part
答案
答案：B
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She ______ the national table tennis team in 1988. [ ]
A. joined in
B. joined
C. took part in
D. took part
答案：B
和L2，其余导线电阻不计．当S闭合时( )