In a Series of Experiments with the Bacteriophage T4, Seymour

In a series of experiments with the bacteriophage T4, Seymour Benzer showed that recombination could take place within a single gene and created the first molecular map of a gene. Benzer used the complementation test to distinguish between functional genes (loci) .
-In complementation tests, Benzer simultaneously infected E. coli cells with two phages, each of which carried a different mutation. What conclusion did he make when the progeny phages produced normal plaques?

A) The mutations were at the same locus.
B) The mutations were at different loci.
C) The mutations were close together on the chromosome.
D) The genes were in the cis configuration.