当\(a\geqslant 2\)时，代数式\( \sqrt {a+1}- \sqrt {a}\)与\( \sqrt {a-1}- \sqrt {a-2}\)的大小关系是\((\) \()\)
A. \( \sqrt {a+1}- \sqrt {a} > \sqrt {a-1}- \sqrt {a-2}\)
B. \( \sqrt {a+1}- \sqrt {a} < \sqrt {a-1}- \sqrt {a-2}\) C. \( \sqrt {a+1}- \sqrt {a}= \sqrt {a-1}- \sqrt {a-2}\) D. 与\(a\)的大小有关
