The question asks which diseases of milching (milk-producing) animals are infectious.

Option 1 includes Foot and Mouth Disease, Authraz, and Black Quarter. Authraz is not a known disease, so this option is invalid.

Option 2 compromises Authraz, Black Quarter, and Cowpox. Again, as Authraz is not recognized, this option is also incorrect.

Option 3 lists Foot and Mouth Disease, and Cowpox, which are both highly contagious diseases among cattle and other cloven-hoofed animals, making this option correct.

Option 4 includes all the diseases, but as already mentioned Authraz is not a known animal disease, so this option is invalid as well.

Overall, the correct answer is option 3, which correctly lists Foot and Mouth Disease and Cowpox as infectious diseases in milching animals.