As we move along the series, we notice that line connected with square box increases by one in each step. Also, the left end of the image at odd positions have one pattern and the left end of the image at even positions have one pattern. So, as the next image in the series is at odd position, the left end of the image will be similar to the pattern of images at odd positions and the number line connected with square box will be 5. Option 3 meets all the conditions.