Answer
The x-component and the y-component are also doubled.
Work Step by Step
Let $\theta$ be the angle from the positive x-axis counterclockwise to the vector $B$. Let $\vert B \vert$ be the original magnitude of the vector.
$x = \vert B \vert ~cos~\theta$
$y = \vert B \vert ~sin~\theta$
If the magnitude of the original vector $B$ is doubled to $2\vert B \vert$, we can find the new values of $x$ and $y$:
$x = 2\vert B \vert ~cos~\theta$
$y = 2\vert B \vert ~sin~\theta$
Therefore, the x-component and the y-component are also doubled.
