The correct answer is option (B) The bacteria can cut the viral DNA at its specific restriction site but protect their own chromosomal DNA by modifying its bases and blocking the restriction enzyme.
Restriction enzymes cleave the double stranded DNA at specific points into fragments. Endonucleases cleave the internal or the non-terminal phosphodiester bonds after recognizing specific sequences on the DNA which are often palindromic. To prevent the destruction of its own DNA by the restriction enzymes, a few specific bases are modified in each strand by the addition of the methyl groups. Bacteria prevent their own DNA from being cut by the restriction enzyme through the methylation of the restriction sites. The process is called the restriction modification system found in the bacteria and other prokaryotic organisms.
