以下部位，除哪个以外都是白屑风的好发部位（）
A.头皮
B.鼻唇沟
C.胸背部
D.腋窝
E.小腿
参考答案：E
在棱长为1的正方体AC1中，点P为侧面BB1C1C内一动点(含边界)，若动点P始终满足PA⊥BD1，则动点P的轨迹的长度为________．
—Hi,Bruce.Here's a letter for you.
—Thanks.I wonder_________.[ ]
A. who that letter was from
B. who was from that letter
C. who was that letter from
D. who from that letter was
