The correct answer to this question is A, water. This question involves an understanding of black magic. Black magic involves the use and practice of supernatural powers or magic for evil and/or selfish purposes - this is a stark contrast the use of white magic.
Black magic usually involves the use of spells and typically consists of utilizing the natural elements. Typically, magic works with five sacred elements: earth, air, fire, water and aether (aka spirit), but the other elements are, too, a part of black magic, often these are opposing forces, in this case thunder being the anthithesis to water.