Introduction:
Electric current is the flow of electric charge in a conductor. It is an important concept in the study of electricity and is measured using a device called an ammeter.

Explanation:
An ammeter is a device used to measure the electric current flowing through a circuit. It is connected in series with the circuit, meaning that the current passes through the ammeter itself. By measuring the current passing through it, the ammeter provides an accurate reading of the electric current.

Other Options:
Let's briefly discuss the other options mentioned in the question:

1. Odometer: An odometer is a device used to measure the distance traveled by a vehicle. It has no relation to measuring electric current.

2. Voltmeter: A voltmeter is a device used to measure the voltage or potential difference across a circuit element. While it is related to electricity, it is not used to measure electric current directly.

3. Galvanometer: A galvanometer is a device used to detect the presence and direction of electric current. It is often used as the basis for constructing ammeters and voltmeters.

Conclusion:
Electric current is measured using an ammeter. It is connected in series with the circuit and provides an accurate reading of the current flowing through the circuit. While other devices such as voltmeters and galvanometers are also used in the study of electricity, they are not directly used to measure electric current.