Lời giải

\( \int e^{2x} f(x) \, dx = x^2 + C \Rightarrow e^{2x} f(x) = 2x \)

\( \Rightarrow  f(x) = \frac{2x}{e^{2x}} \Rightarrow f'(x) = \frac{2 . e^{2x} - 4x . e^{2x}}{(e^{2x})^2} = \frac{2 - 4x}{e^{2x}} \)

\(\Rightarrow \int_{1}^{2} e^{2x} f'(x) \, dx = \int_{1}^{2} (2 - 4x) \, dx =  2x - 2x^2  \bigg|_{1}^{2}  \)

\(= -4 - 0  = -4 \)

\(\Rightarrow\) Vậy chọn đáp án \(\boxed{\text{B}} \)