— The classroom is ______ clean ______ it was yesterday.— Sorry, I forgot to clean it.
A：as; as
B：so; as
C：not as; as
D：more; than
在NaCl、NaOH、N2、CO2中，只含有离子键的是 ____，只含有极性键的是 ____，只含有非极性键的是 ____，既含有离子键又含有极性键的是 ____
