①地貌的酷似造型,只能在特定的观赏点才能获得某种形象
②山中的峡谷、洞、一线天景观,要置身其中远观方知其妙
③瀑布景观,宜在适当距离俯视
④观赏江河湖海应在位置较高的亭台楼阁之上
A:①②
B:③④
C:①④
D:①②③
— Come and join us, Ben!— I'm afraid I can't. I'm too busy now. If I ________ time, I would certainly go.
多项式-5mx3+25mx2-10mx各项的公因式是( )