问题
选择题
Jenny was looking for a seat when, luckily, a man _____ and left.[ ]
A. took up
B. got up
C. shut up
D. set up
答案
答案：B
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Jenny was looking for a seat when, luckily, a man _____ and left.[ ]
A. took up
B. got up
C. shut up
D. set up
答案：B
和二极管D。二极管D具有单向导电性，即正向电阻为零，反向电阻无穷大。下列说法正确的是 
