Determine Which Number/s in the Set Is/are Natural Number/s

Multiple Choice

Determine which number/s in the set is/are natural number/s. ​
{2) 91, 0.684..., -6, 0.017632482..., 40, -16}
​

A) 40, -16
B) 2.91, 0.684..., -6, 40, -16
C) -6, 40, -16
D) 0.017632482...
E) 40