Explanation:

- CPM (Characters Per Minute): Used to measure the speed of printers, particularly dot matrix printers. It counts the number of characters printed in a minute.

- PPM (Pages Per Minute): Commonly used for laser and inkjet printers. It indicates how many pages a printer can print in one minute.

- LPM (Lines Per Minute): Often used for line printers. It measures the number of lines a printer can print per minute.

- Correct Answer: Option 4 - All of the above. Each unit relates to different types of printers or printing measurements.