系统性硬化症的病理特点是
A.中、小动静脉血管炎
B.滑膜炎
C.肌炎
D.胶原增殖、纤维化
E.肌腱端炎
参考答案:D
Would it be _____ for you to pick me up at four o'clock and take me to the airport? [ ]
A. free
B. vacant
C. handy
D. convenient
试述哺乳动物骨骼系统有哪些特点?