1-80%=20%;
答:还有20%没有卖.
故选:A.
A.O点电场强度为零
B.D点电场强度为零
C.若将点电荷+q从O移向C,电势能增大
D.若将点电荷-q从O移向C,电势能增大
–Who can reach the dictionary on the top shelf?
–Susan can. She is ________girl of us all.
A. taller B. a tall C. the tallest