In the given question , LU is a set of strings which are accepted by the Universal Turing Machine..In order words , these are the strings in which the given Turing machine halts and each of the string of LU has this property..In other words , LU represents a recursive language (or a recursive set)..
Now given reduction : L ≤ LU
Now we know that for easy problems (or) languages [ REC (or) decidable , RE , P , NP ] , reduction works right to left i.e. if the class of the right part of the reduction is known , then we can deduce the left part also..But other way round , we cannot conclude anything..
As here , LU is a recursive language , so due to the reduction : L ≤ LU , L is recursive as well..
Hence option C) should be correct..