在思想品德课上，王老师讲到竞争与合作的关系时，给出了这样一个公式让同学们去思考：1+1-?
王老师：“1+1=2”这在数学常规计算中是非常简单的，但在社会生活中的算法也是这样吗?
小宇同学：在某种情况下，1+1>2;而在另一种情况下，1+1<2。
阅读后，请回答：

$+\frac{1}{{(n+1)}^2}$ ．设 $S=\sqrt{S_1}+\sqrt{S_2}+$ … $+\sqrt{S_n}$ ，则S=____ （用含n的代数式表示，其中n为正整数）．

下列关于生态系统稳定性的叙述中，不正确的是(　    )

A: Hey, Peter. ____ 
B: I argued with my best friend. ____ 
A: Well, you could write him a letter.
B: I don't think so. I don't like writing letters.
A: ____ .
B: No, I don't want to talk about it on the phone.
A: Well, you should say you're sorry.
B: Yes, I know I should, but it's not easy.
A: Hey, I know. You could give him ____  a ball game.
A: Well, that's a good idea, but ____ .