A:for which
B:at which
C:with which
D:with which
如图,长为2l的直导线折成边长相等,夹角为60°的V形,并置于与其所在平面相垂直的匀强磁场中,磁感应强度为B.当在该导线中通以电流强度为I的电流时,该V形通电导线受到的安培力大小为( )
As the smallest child of his family, Alex is always longing for the time _______ he should be able to be independent.
开创了“开元盛世”局面的皇帝是( )