The maximum number of 90° angles between bond pair of electrons is observed in

The graph of the function y = f(x) is symmetrical about the line x = 2, then

The range of the function f(x) = $${}^{7 - x}{P_{x - 3}}$$ is

If $$f:R \to S$$, defined by
$$f\left( x \right) = \sin x - \sqrt 3 \cos x + 1$$,
is onto, then the interval of $$S$$ is