Explanation:

- Option 1: Murder typically refers to the unlawful premeditated killing of one human being by another. However, abetment of murder is a different legal concept, which involves encouraging or facilitating someone to commit murder, making Option 1 correct on its own.

- Option 2: Murder committed under a threat of instant death might fall under the defense of duress, which can be complex in legal systems. Typically, murder is not excused because someone was under threat, so Option 2 is also correct on its own.

- Option 3: Both (a) and (b) acknowledges that both previous statements are relevant and correct.

Answer: Option 3

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