不属于老年病特点的是
A．临床症状及及体征不典型B．多种疾病共存C．病程长、病情重D．易发生水、电解质紊乱E．营养缺乏
参考答案：E
Half of his homework ________ wrong. [ ]
A. is
B. are
C. have
D. has
在抗压强度相同的条件下，轻骨料混凝土干表观密度比普通混凝土低( )。
A．15%～30% B．20%～40%C．25%～50% D．30%～60%
