018.
I remember that when I was in my teens, I used to disobey many rules my parents told me. For example, when I kept on playing jazz records on the record player, my father used to criticize such music as noise and replace them with disks of classical music that I always considered extremely dull.
My parents were also very particular about the friends I went out with, always warning me that "one rotten apple could ruin a whole basket of apples." When I wanted to sleep with my pet dog Peppy, they immediately said NO because they thought that I would be bitten by fleas.
Today, however, I am also the father of a boy of fifteen, and I find that I, too, am pressuring my son with a lot of rules that he seems to find hard to follow. The other day, I noticed that my son's hair was too long, so I told him to have it cut short. Ordinarily, he is fairly obedient, but this time he put his foot down.
"What's wrong with long hair?" he said, "All my friends have long hair. And besides, it's my own hair, isn't it? I don't think you have the right to order me to cut it short, even if you're my father!"
When I was a boy, if I had spoken like this to my father, I know that he would have given me a good beating. But I suddenly realized that we are now living in a more liberal world, and that my son's wearing his hair long was merely an example of the generation gap that existed between us. So I gave in, and so he still wears his hair long.

答案解析：
(1) 正确答案为C。根据classical music that I always considered extremely dull. 我认为古典音乐非常无聊。可知，作者认为古典音乐很无聊，因此C项正确。
(2) 正确答案为A。根据My parents were also very particular about the friends我父母对我的朋友也很挑剔，可知，作者的父母对他说“一颗老鼠屎坏了一锅粥”是怕儿子的朋友对他有不好的影响，因此A项正确。
(3) 正确答案为C。根据he put his foot down. put one's foot down的意思是拿定主意阻止；执意反对；可知，当作者要求他的儿子把头发剪短时，遭到了儿子的坚决反对，因此C项正确。
(4) 正确答案为B。根据an example of the generation gap that existed between us这就是我们之间存在代沟的例证。可知，最适合这篇文章的标题为代沟，因此B项正确。