After retirement, Mr. Smith ______ painting, which he had always loved but had not had time for.

A．took up

B．got up

C．help up

D．looked up

许多人喜欢晨练，但从环境角度来看，城市早晨的空气并不新鲜，原因是（）

A.早晨空气中有时有逆温层，不利于污染物的扩散

B.早晨空气中含有大量的二氧化碳

C.早晨公路上汽车太多，污染严重

D.早晨人们刚刚起床，不适宜在室外锻炼