Answer:
Top right figure (the trapezoid)
Explanation:
Line symmetry means that if you draw a line that cuts the figure, and reflect the figure across that line, the figure does not change.
Now, if we use vertical lines, a figure will have a line symmetry if it is exactly the same in the left as it is in the right.
And we can see that none of the figures meets this condition.
If instead, we use horizontal lines, then the figure must be equal above and below.
Particularly the "L" and the "t" can be discarded.
Also, the bottom right image can be discarded, as the bottom is clearly different than the top.
But the top right figure (the trapezoid) is exactly the same in the bottom as in the top, so if we reflect that image across a horizontal line that cuts it in two halves, the figure will not change, so that is the figure that has line symmetry,