The correct answer is: b) Chief Minister.
The Chief Minister is the head of the executive branch of the Mizoram government. He/She is the leader of the party or coalition that has the majority of seats in the Mizoram Legislative Assembly. The Chief Minister is appointed by the Governor of Mizoram and holds office for a term of five years.
The Governor is the head of state of Mizoram. He/She is appointed by the President of India for a term of five years. The Governor has the power to dissolve the Legislative Assembly, appoint the Chief Minister, and dismiss the Council of Ministers.
The Speaker of the Assembly is the presiding officer of the Mizoram Legislative Assembly. He/She is elected by the members of the Assembly and holds office for a term of five years. The Speaker has the power to maintain order in the Assembly and to decide on the admissibility of motions and amendments.
The Chief Secretary is the head of the Mizoram Civil Service. He/She is appointed by the Governor on the advice of the Chief Minister. The Chief Secretary is responsible for the administration of the state and for the implementation of the policies of the government.