My friend is ________ years old. Today is his ________ birthday.
A:ten; tenth
B:tenth; ten
C:ten; ten
D:tenth; tenth
⑴无理数就是开方开不尽的数;
⑵无理数是无限不循环小数;
⑶无理数包括正无理数、零、负无理数;
⑷无理数是无限不循环小数.