does anyone know this?

Answer:
B. 7^5/4
Step-by-step explanation:
[tex] \sqrt[4]{7} \: . \: \sqrt{49} \\ = \sqrt[4]{7} \: . \: 7 \\ = {7}^{ \frac{1}{4} } \: . \: {7}^{ \frac{4}{4} } \\ = {7}^{ \frac{1}{4} + \frac{4}{4} } \\ = {7}^{ \frac{5}{4} } [/tex]