第551题:选择
已知一个自然数的算术平方根为a(a>1)a(a>1)a(a>1) ,则与这个自然数相邻的两个自然数的算术平方根分别是( ).
A. a−1,a+1a-1,a+1a−1,a+1
B. a2−1,a2+1\sqrt{a^2 -1},\sqrt{a^2 +1}√a2−1,√a2+1
C. a−1,a+1\sqrt{a-1},\sqrt{a +1}√a−1,√a+1
D. a2−1,a2+1a^2 -1 ,a^2 +1a2−1,a2+1