Restriction endonucleases, when present in a host cell act on foreign DNA molecule and cleave them, but they do not act on host DNA molecule. It happens because:

(A) Restriction endonuclease cannot act on host DNA
(B) Host DNA is packed into chromosom
(C) Host DNA is methylated hence restriction endonucleases can’t act.
(D) Restriction endonucleases become inactive when they reach host DNA