With reference to the Theravada school of Buddhism, consider the following statements:

1. Sthaviravadins belong to Theravada.

2. The Theravada form of Buddhism gradually spread eastward, becoming dominant in Myanmar in the late 11th century and in Cambodia and Laos by the 13th and 14th centuries.

3. It is the dominant form of religion in Cambodia, Laos, Myanmar, Sri Lanka, and Thailand.

How many of the above statements are correct?