Fill in the blank with the appropriate modal from the options given:

You _____ serve your country with pride.

ought to

The correct answer is Option (3) → ought to

1. Could: This modal expresses possibility or ability but does not convey a strong sense of obligation or duty.
2. May: This modal indicates permission or a possibility, which doesn't emphasize the idea of serving with pride.
3. Ought to: This modal expresses moral obligation or duty, making it the best choice for conveying the idea of serving one's country with pride.
4. Would be: This phrase is not a modal verb and doesn't fit grammatically in the context of expressing obligation or advice.

So, the complete sentence would read: "You ought to serve your country with pride."