Answer: D. He did not cause her death.
Explanation:
In a situation whereby the husband is prosecuted for the murder of his wife, the reason why he would be acquitted I because he didn't cause her death since the autopsy revealed that she died of cancer.
Murder is when someone is unlawfully killed by another person. In this case, the husband's action isn't the cause of her death.
Even if the husband didn't give her the poison, she'll still die. Therefore, the action of the husband were not the cause of the death.