Trouble with lucky guesses is that I have to think up a new question.
What connects the following names:
{a} Munro, Chattan and Mackinnon;
{b} Buchanan, MacDonald, MacGregor, MacKintosh, MacLeod;
{c} Campbell, Fraser, Stewart and Mackenzie;
And into which group, {a}, {b} or {c} would Cameron go?