Answer:
D
Explanation:
These are transformations. One thing to remember is that only a sign change (like a negative sign on the new function) will change the direction in which the parabola opens.
Here, going from f(x) to 1/2 * f(x) has no sign change, so the parabola will open in the same direction as before. Eliminate A and C.
Vertical transformations are those that are done to the entire function, as opposed to horizontal transformations which are done only on the x. Here, since we're multiplying 1/2 to f(x), we have a vertical transformation.
There are different transformations. The one here would be a vertical shrink by a factor of 1/2. Vertically shrinking a function is basically the same as compressing it, which would make it wider.
The answer is thus D.