一般来说，砂土、粘土、壤土总孔度从大到小排列顺序为（）、（）、（）。
参考答案：粘土；壤土；砂土
将氯化铵固体溶解在D2O（重水）中，反应的离子方程式正确的是
A．NH4+ + D2O NH3·D2O + H+
B．NH4+ + D2O NH3·HDO + D+
C．NH4+ + 2D2O NH3·HDO + D3O+
D．NH4+ + 2D2O NH3·D2O + HD2O+
On his way to the airport，it ________him all of a sudden that he had forgotten his passport.
A．hit
B．knocked
C．occurred
D．beat
NH3·D2O + H+