Double derivative concavity question

I am working on a practice problem where I am asked to identify concavity through the use of double derivatives.

The equation: f(x)=2x^4−8x+1

After working the problem out, the double derivative is positive across the entire equation, except for a point at zero where f''(0) = 0.

How should the concavity be described (and if you would explain why the correct one is correct that would be great).

(-∞, ∞)

or

(-∞, 0)∪(0, ∞)