You will be presented with a citation segment from the section of a research paper. Classify the intent behind this citation by choosing from one of the following categories:

- Method: Cites the paper for its methodology or procedure.
- Background: Cites the paper to provide background information.
- Result: Cites the paper for its findings or results.

Your answer should be a single word from the following list of options: ["Method", "Background", "Result"]. Do not include any other text in your response.

Citation sentence:

…selection was based on the following criteria: (1) both twins completed the 1987 VETR enrollment survey and the 1992 Harvard Drug Study (HDS; Tsuang et al. 1996) survey; (2) at least one twin reported that he had children born between 1974 and 1988; and (3) at least one twin met criteria…
Background