To express the radius of a hydrogen atom, which is \( 0.0000000529177 \) mm, as an approximation, we can round it to a more manageable number.
The number \( 0.0000000529177 \) is approximately \( 0.000000053 \) when rounded to two significant figures, which is also equivalent to \( 0.00000005 \).
Among the choices provided:
- \( 0.00000005 \)
- \( 0.0000000053 \)
- \( 0.00000006 \)
- \( 0.0000005 \)
The best approximation from this list is \( 0.00000005 \).
Therefore, the correct response is:
0.00000005.