根据句意及首字母提示在横线处填上恰当的单词，使句子意思完整，语法正确。

1. The Y______River is the second longest river in China, and it is also called "Mother River of  China".

2. Her story broke my h_______and I felt very sad.

3. The work doesn't s_______me fine.I can't do it.

4. I e_______I will get good grades in the next exam.

5. My parents always ask me not to tell lies and be an h_______child.

在半径为R的半圆内，内接一个矩形，求矩形边长为何值时，矩形的周长最大。并求最大周长。