若a-7与-2互为相反数，则a的值为 [ ]
A．3
B．5
C．7
D．9
答案：D
骨与软组织疾病一般首选的影像学检查方法是（）。
A.透视
B.X线
C.超声
D.CT
E.MRI
Shakespeare's ______ are mainly written under the principle that national unity under a mighty and just sovereign is a necessity.
A. history plays B. tragediesC. comedies D. plays
