Which option completes the puzzle?
Looking at each row, the second box is the first box flipped vertically, so the answer must be the first box in row 3 flipped vertically i.e. answer (1).
It can be difficult to visualize the result of flipping a shape vertically. The diagram below shows the boxes in column 1 of the question and above them the result of flipping these boxes vertically.
Flipping the boxes vertically is the same as reflecting them in the red mirror line shown in the diagram above.
Another (possibly easier) way of visualizing a vertical flip is to think of it as flipping or turning a page in a book upward about the central spine part of the book.
If you prefer to visualize a vertical flip as a reflection, then to work out the result of the reflection, note that the reflected point is the same distance from the mirror line as the original point on a straight line that is perpendicular to the mirror line. Examples of a point A and its reflection, point A’, and a point B and its reflection, point B’, are shown below.