The correct answer is (a). The husband or wife of the accused is a competent witness in criminal proceedings. This is because the marital privilege does not apply in criminal cases. The marital privilege is a rule of evidence that prevents a spouse from being compelled to testify against the other spouse in a civil case. However, this privilege does not apply in criminal cases because the government has a greater interest in ensuring that the truth is brought out in criminal trials.
Option (b) is incorrect because the husband or wife of the accused is a competent witness. Option (c) is incorrect because the husband or wife of the accused does not need the consent of the other spouse to testify. Option (d) is incorrect because the husband or wife of the accused does not need to be sane to testify.