Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to use footprints in detecting [title] Observe the footprints. [step] Get yourself a good magnifying glass for the finer details, or at least good eyesight for spotting the footprints. [title] Measure the footprints.

Ending1: [step] Place the nose, hand, body and left hand prints on a sheet of paper or a sheet of cardboard. If the tracks indicate how well they have made their way through the water, that can make spotting them a lot easier. Ending2: [step] Place the eyeglass over the puddle of muddy water, then move it along the board where the tracks are. If they move in a straight line, tap the glass until the ice crystals and mud dissolve. Ending3: [step] The size of a person's shoe usually gives the height of the person to a given range. This ratio is rather accurate; however there is a certain percentage of the population, around 10-20%, which this deduction would not apply. Ending4: [step] Use a measuring tape to subtract 1/2 inch (1.3 cm) from the height and width measurements for each footprint. [substeps] Have the foot measure measured first, then draw a circle next to the foot to mark the foot size.

Answer format: ending1/ending2/ending3/ending4