A mutant strain of $T_4$ – Bacteriophage, R-II, fails to lyse the E-Coli but when two strains $R-II^X$ and $R-II^Y$ are mixed then they lyse the E.Coli. What may be the possible reason : -

Question

( A ) Bacteriophage transforms in wild
( B ) Both strains have simillar cistrons
( C ) Both strains have different cistrons
( D ) It is not mutated