Option B is correct option.
Step-by-step explanation:
We need to find Which of the following rational exponent expressions is NOT simplified correctly as a radical expression.
Option A , C and D are correctly simplified.
Option B is NOT correctly simplified.
Reason:
We are given: 
Expressing into Radical Expression we get:
![x^{\frac{7}{4}}=\sqrt[4]{x^7}](https://tex.z-dn.net/?f=x%5E%7B%5Cfrac%7B7%7D%7B4%7D%7D%3D%5Csqrt%5B4%5D%7Bx%5E7%7D)
So, Option B is correct option.
Keywords: Radical Expression
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