d. to be talking
happen to do something.
happen to be doing something
指恰好在做某事。这里用happened to be talking而不用happened to talk是因为强调当时他被石头打中的那一“时刻”我“正在”跟他讲话
d,happen to do something
A ...我很意外我和他谈话的时候他被石头砸中了..嘻嘻
选C,原句意思为我偶然跟他说话当他被石头击中时,sb hanppen to就是偶然的意思
C