Sam is training for the marathon. He drove 12 miles from his home to the Grey Hills Park and then ran 6 miles to Red Rock, retraced his path back for 2 miles, and then ran 3 miles to Rock Creek. If he is then n miles from home, what is the range of possible values for n ？（）

A. 1≤n≤23

B. 3≤n≤21

C. 5≤n≤9

D. 6≤n≤18

E. 9≤n≤15

门静脉主干由下列哪几条静脉汇合而成（）

A.肠系膜上静脉和门静脉左支

B.门静脉左、右支

C.脾静脉与肠系膜上静脉

D.右肾静脉和门静脉右支

E.右肾静脉和门静脉左支