Is that a good age to be?

应该是这样：
is that a age to be a good age?的另一种表达方式.
有to be的意义:对"好年龄"的范围限定.
a good age to be (at)--- 想处在(喜欢拥有)的好年龄
a good age to learn English ---学英语的好年龄
a good age to marry ---结婚的好年龄
没有to be "好年龄"就没有限制了,泛指.