— Please sit down. () — _____________.
A:Hello
B:Thank you
C:Sit down
D:I’m fine
Remember that ______ is better than cure, so brush your teeth at least twice a day and visit your dentist for regular check-ups.
如下图所示,天花板上的电线吊着一盏电灯,在下列各对力中,属于平衡力的是()