16的算术平方根是( )
A:4
B:±4
C:±2
D:2
There is _______ park in my village, and I go to _______ park every week.
如图所示,利用滑轮沿水平方向匀速拉动物体A前进时,若绳子自由端拉力F=90N,物体A重1500N,不计滑轮重和绳与滑轮间摩擦.