Concept: Electrolysis is investigated using a device that measures the chemical effect of an electric current.
Explanation:A voltameter, also called an electrolytic cell, is the correct instrument for studying electrolysis.
It measures the quantity of a substance deposited or liberated during electrolysis.
This allows the experimenter to relate the charge passed to the chemical change occurring.
In contrast, a voltmeter measures potential difference, an ammeter measures current, and a galvanometer detects small currents.
Therefore, only the voltameter is used to investigate electrolysis.
Answer: D. Voltameter