The reflection of the point (a, β, γ) in the xy-plane is

The correct option is (α, β, γ).

To understand the reflection of a point in three-dimensional space, let us review the rules for reflecting a point across the coordinate planes:

When a point is reflected across a coordinate plane, the coordinates that lie parallel to the plane remain unaffected, whereas the coordinate perpendicular to the plane reverses its sign (is multiplied by -1).

For a reflection in the xy-plane:
1. The $x$-coordinate remains unchanged.
2. The $y$-coordinate remains unchanged.
3. The $z$-coordinate changes its sign.

If we start with a point whose vertical distance below the xy-plane is represented by a negative $z$-coordinate, namely $-\gamma$, reflecting this point across the xy-plane will negate the $z$-coordinate, transforming it from $-\gamma$ to $\gamma$.

Thus, the coordinates of the reflected point in the xy-plane are:
$(\alpha ,\beta ,\gamma )$