In a data dependency graph, what can you tell from the number of edges that enter a node corresponding to a statement S? (a) This is the number of variables appearing in the statement S. (b) This is the number of statements which use the values of variables set by the statement S. (c) This is the number of statements which assign values to variables, where those values may be used in the execution of statement S. (d) This is the number of variables whose values are used in the execution of statement S.