Hello There!
[tex]8.7 * 10^{-5} [/tex] is in standard index form.
Standard form is when it is the original number
The '-5' as a power means you need to shift the zero back 5 spaces.
Or, divide by 100,000.
If you do this, you would get 0.000087.
Thus, making it option B.
Hope This Helps You!
Good Luck :)
- Hannah ❤