Explanation:

- Option 1: Murder ordinarily refers to the unlawful premeditated killing of one human being by another. It does not include the abetment of murder, which is a separate charge related to encouraging or assisting another person in committing murder.

- Option 2: Even if a person commits murder under a threat of instant death, it is generally not excused. Legal systems often require that extreme duress be considered in the context of self-defense or other legal defenses rather than providing a complete excuse for murder.

- Option 3: Both of the statements in Options 1 and 2 are correct, as described.

- Option 4: This choice would mean that neither statement is correct, which isn't true here.

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