Answer: Option 3.
Option 4. ![(\sqrt[c]{a} )^b](https://tex.z-dn.net/?f=%28%5Csqrt%5Bc%5D%7Ba%7D%20%29%5Eb)
Step-by-step explanation:
concept to know: when the exponent is a fraction, the numerator will be the real exponent with the base (i.e 7^5), while the denominator will be the root
----------------------------------

b is the numerator which means it will result in 
c is the denominator which means it will result in ![\sqrt[c]{a}](https://tex.z-dn.net/?f=%5Csqrt%5Bc%5D%7Ba%7D)
The combination of this two will be ![\sqrt[c]{a^b}](https://tex.z-dn.net/?f=%5Csqrt%5Bc%5D%7Ba%5Eb%7D)
This will also be presented as ![(\sqrt[c]{a} )^b](https://tex.z-dn.net/?f=%28%5Csqrt%5Bc%5D%7Ba%7D%20%29%5Eb)
Hope this helps!! :)
Please let me know if you have any question