Choose the correct phrase from the given option and make a conditional sentence. If he forgot about it, I ______ remind him.

The correct answer is "Option 4" i.e. 'would.'

 Key Points

• This is an example of the second conditional sentence (द्वितीय संयोजन वक्य), which is used to talk about things that are unreal (not necessarily true) or express hypothetical situations in the present or future.
• Example: "If I saw her, I would say hello."
• Here, the correct word 'would' (चाहिए) expresses a hypothetical situation where if he forgets, then I would remind him.

Therefore, the correct answer is - Option 4 "would."

 Additional Information

• 'Have' is incorrect as it's used to talk about experiences or completed actions.
• 'Had' and 'will' are also incorrect as they do not appropriately express the hypothetical situation.