Separability is free in all four settings

1. A.If K is the splitting field of a non-constant polynomial over $\mathbb{Q}$, then K is Galois over $\mathbb{Q}$.✓ Correct
2. B.If K is a normal extension of $\mathbb{Q}$, then K is Galois over $\mathbb{Q}$.✓ Correct
3. C.If K is the set of all the roots of the polynomial $x^{121} - x$ in an algebraic closure of 𝔽$_{11}$, then K is Galois over 𝔽$_{11}$, where 𝔽$_{11}$ is the field with 11 elements.✓ Correct
4. D.If $K = \mathbb{Q}(2^(1/13), \zeta_{13})$, where $\zeta_{13}$ is a primitive 13th root of unity in $\mathbb{C}$, then K is Galois over $\mathbb{Q}$.✓ Correct

The trap it tests

A theorem applied without checking one of its preconditions.