4.
The answer is: B
Explanation
The correct option is B: Two.
According to Section 120A of the Indian Penal Code, 1860 (I.P.C.), criminal conspiracy is an agreement between two or more persons to do an illegal act, or a legal act by illegal means.
This is also the general definition of conspiracy in most U.S. jurisdictions. Therefore, conspiracy needs at least two persons who have the intention and agreement to commit an unlawful act.