Choose the correct answer.

The function f(x) = |cos x| is

Choose the correct answer.

Let f(x) = |cos x|. Then,

Choose the correct answer.

The function f(x) = 1 + |cos x| is

Choose the correct answer.

The function where [.] denotes the greatest integer function, is

Choose the correct answer.

Let f(x) = a + b |x| + c |x|⁴, where a, b, and c are real constants. Then, f(x) is differentiable at x = 0, if