Concept:A contingency warrant authorises urgent spending for unforeseen emergencies such as natural disasters.Explanation:Natural disasters are sudden, unexpected events.Their expenses cannot be postponed for routine approval.Virement is not possible when the need is urgent and unplanned.So, a contingency warrant lets the Accountant-General release funds immediately for this purpose.Hence, the authority to spend on a natural disaster is provided by this warrant.Answer:A. contingency warrant