下列不属于多基因遗传病的特点是（）
A.由多对基因控制
B.常表现出家族聚集现象
C.易受环境因素的影响
D.发病率极低
参考答案：D
对生产有重要意义的重介质悬浮液的性质一是悬浮液的密度及其稳定性、二是悬浮液的粘度及流变性。
__________ was known to us all that Tom had broken his promise __________ he would give each of us a small gift.
A．It; that
B．What; that
C．As; which
D．It; which
