It's already 10 o'clock. I wonder how it________that she was two hours late on such a short trip.
A:came over
B:came out
C:came about
D:came up
我国青藏高原形成广大的高原山地气候,影响气候形成的主要因素是( )
沙漠地区的植物通常有很发达的根系和较小的叶片,与此相关的主要因素是( )