He ____ to Jack’s house when I saw him yesterday.

Answer: Was going

Explanation: The sentence describes an action that was in progress at a specific time in the past ("when I saw him yesterday"), so the past continuous tense is used.

• Rule: Use past continuous (was/were + verb-ing) for an action that was ongoing at a past moment.

• Subject-verb agreement: "He" is singular, so use "was" rather than "were."

• "Were going" is incorrect because it requires a plural subject or 'you/we/they'; it does not agree with the singular subject "He."

• "Is going" and "Are going" are present continuous forms, so they do not match the past-time reference "yesterday."