三时计算法简介：Cheng Keshu lowered her head and concentrated on doing the after-school exercises in the history book. Her white fingers held the pen tightly, and her delicate handwriting appeared neatly on the book. She was working on a key question.
Cheng Keshu lowered her head and concentrated on doing the after-school exercises in the history book. Her white fingers held the pen tightly, and her delicate handwriting appeared neatly on the book. She was working on a key question.
