To express the radius of a hydrogen atom, which is given as \(0.0000000529177\) millimeters, as an approximation, we can round it to a more manageable figure.
Looking at the digits:
- The number is \(0.0000000529177\).
- We can approximate it to \(0.00000005\) when rounding to the nearest significant figure.
Thus, the best approximation from the options provided is:
0.00000005