You may have known someone else for ten years and yet he will ne

You may have known someone else for ten years and yet he will never be more than a casual __________.
A、friend
B、colleague
C、acquaintance
D、associate
【正确答案】：C
【题目解析】：认识了十年了，表明认识时间之久，本应该十分熟悉，但是句子后面有转折，说明并不熟，C项：熟人，符合题意。