单项选择。

He ______ up early every morning. But he ______ up late this morning. [ ]

A. get, got

B. gets, gets

C. got, gets

D. gets, got

时间数列加法模型假定四种变动因素是相互独立的，而乘法模型假定四种变动因素存在着相互影响，两种模型的假定有着原则区别。