在皮肤血管炎的各种病因中属特发性所占比例为（）。
A.30%
B.15%～20%
C.10%～20%
D.5%
E.45%～55%
参考答案：E
焊条由焊芯与（）组成；
Lucy liked all the dresses there, but she took the ______one to save as much money as
possible for Project Hope.
A．cheaper
B．more expensive
C．cheapest
D．most expensive
