税收征收管理的中心环节是（）。
A.税款征收
B.税务登记
C.税务稽查
D.纳税申报
参考答案：A
— I rang you at about nine, but there was no reply.
— Oh, that was probably________I was seeing the doctor. [ ]
A. why
B. when
C. what
D. that
一杯水的比热容是4.2×103J/（kg-℃），它表达的物理意义是______．若将此杯水倒掉一半，剩下半杯水的比热容是______，若水凝固成冰则比热容______（填“改变”或“不变”）．
