下列疾病紫癜的原因为血小板异常的是（）
A.过敏性紫癜
B.药物性紫癜
C.机械性紫癜
D.血小板无力症
E.血友病
参考答案：D
I often ________ the words I don't know in the dictionary or on the Internet.[ ]
A. look up
B. look at
C. look for
D. look into
