Explanation:

- Option 1: It's not possible to convict three out of five constructively.

- This is true because constructive liability under certain laws requires action with a common intent, typically needing more than just a minority of participation.

- Option 2: For Section 149, there must be at least five persons.

- This statement is correct too. Section 149 of the Indian Penal Code requires unlawful assembly, defined as a group of five or more people with a common objective.

- Option 3: Both (a) and (b).

- Since both statements are accurate, this option is also correct.

- Option 4: None of the above.

- This option is incorrect since both other statements hold true.

The correct answer is Option 3: Both (a) and (b).

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