This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to read an ekg
Understand the grids of an ekg paper printout.
Voltage-the electrical signals of the heart-is measured along the vertical axis; time is measured along the horizontal axis in squares. There are large squares that are divided into smaller squares.

Select from the following. (1). Simply multiply the number (letters together) under each square-this means that there are at least 12 squares of the printout. Measurement of time is dependent on the number of squares of the printout.. (2). Common table sizes of graph paper are ods scale taken at work, lolus scale taken at home, etc. The grids let you view peaks and valleys, as shown in the image.. (3). Small squares are 1 mm across and represent 0.04 seconds. The large squares measure 5 mm across and represent 0.2 seconds.. (4). Double check each set of squares to make sure that the comparison is accurate. Check the denominator within each square for accuracy..
The answer is:
(3).