Nokia, the world's largest mobile phone maker, said that over the first nine months of the year it _____ 23 million handsets in China, an increase of 77 percent _____ the same period a year ago. 

A．sold; comparing with

B．has sold; compared to

C．had sold; compared to

D．was selling; compared with

一个物体受到三个力的作用而做匀速直线运动，已知其中两个力的大小分别为12N和8N，则第三个力的大小不可能为

A．4N

B． 8N

C． 20N

D．30N