Right Answer is: B
The given sentence is an exclamatory sentence. An exclamatory sentence makes a statement that conveys strong emotion or excitement. In such sentences, the reported speech also starts with the word “what” and it shows the degree of emotions to be great. While converting such sentences in indirect speech, the reporting verb is taken as “exclaimed”. We use the word “very” to show the degree to be great. Out of the given alternatives, only option B is the correct conversion.