矿化度是水中所含无机矿物成分的总量,经常饮用低矿化度的水会破坏人的体内()和碱土金属离子的平衡,产生病变,饮水中矿化度过高又会导致()疾病。
参考答案:碱金属;结石症
In terms of the knowledge of science, few students in our class can really ______ Christopher. [ ]
A. suit
B. compare
C. win
D. match
简述挫折产生的原因