The domain of the function $$f: R \rightarrow R$$ defined by $$f(x)=\sqrt{x^2-7 x+12}$$ is
- A$$(-\infty, 3] \cap[4, \infty)$$
- B$$(-\infty, 3] \cup[4, \infty)$$
- C$$(3,4)$$
- D$$(-\infty, 3] \cup(4, \infty)$$
✓ Correct answer: B
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