The function given to us is :
![f(x) = {(x)^7}](https://img.qammunity.org/2019/formulas/mathematics/high-school/97fl3i3k77d1amq4k06haj4r65x9ctxxyr.png)
We want to see which function represents the horizontal compression of f(x) by a factor of 4
We can compress a function horizontally by multiplying the x by a constant number, in this case multiplying x by 4
So horizontal compression of
![f(x) = {(4*x)^7}](https://img.qammunity.org/2019/formulas/mathematics/high-school/x4jlhmbjuvp1z6n5wllpkfc9fk1r58pc65.png)
This matches with the option B =
![r (x) = {(4*x)^7}](https://img.qammunity.org/2019/formulas/mathematics/high-school/21c43xpfjijass7v9iybgysdeiqg6pfh9r.png)
Hence, your answer (B) is correct.