A. Complete nonsense. When even BB is afraid to let her go bc she would turn him to stone immediately, you know that you can't protect yourself with haki. Especially not Coby, if not even BB, Devon or Vasco can do it.
B. Nonsense, too. If guys like Vasco and Cevon can't block it, Coby can't do it either. On top of that Oda would've shown it, if he pulled off sth like that, bc he loves to hype Coby.
C. Most likely option.
Point still stands that Coby wouldn't stand a chance against Hancock anyway. He's (probably) not some completely asexual guy like Luffy and once he has to go closer to Boa, he would be extremely vulnerable to her merow-merow attacks. On top of that we've seen that she's a very capable close-combat fighter who mastered all three types of haki.