Over the past decades, the population in this country      because of the rising birth rate, immigration and the declining death rate.

A．has been increasing

B．have been increasing

C．had increased

D．have increased

如图（a）所示的撑杆跳高主要表示力能使物体发生______；如图（b）所示，光滑的斜面顶端放一小铁球，底端放一磁铁，当小球从顶端滚下时会向______（选填“靠近”或“远离”）磁铁的方向偏，这是因为力可以改变物体的______．