— Well, they have set out to deal with the present situation ________ they think deserves their immediate attention.
A:what
B:where
C:when
D:which
求四边形ODPC的面积.
磁体旁小磁针静止时所指的方向如图丙所示,画出通过小磁针中心的一条磁感线,并标出磁体的N、S极.
关于安全用电,下列说法中正确的是( )