A、A plan should not be made until you are 30. B、A plan of ten years of time is the key to success. C、A plan is necessary but not

Leonard Bernstein said that to achieve great things, you need a plan and not quite enough time. Isn’t that true? So what do you think happens when you pat a twenty something on the head and you say, "You have 10 extra years to start your life"? Nothing happens.
    You have robbed that person of his urgency and ambition, and absolutely nothing happens. And then every day, smart, interesting twentysomethings like you or like your sons and daughters come into my office and say things like this: "I know my boyfriend’s no good for me, but this relationship doesn’t count. I’m just killing time." Or they say, "Everybody says as long as I get started on a career by the time I’m 30, I’ll be fine." But then it starts to sound like this: "My 20s are almost over, and I have nothing to show for myself. I had a better résumé the day after I graduated from college." And then it starts to sound like this: "Dating in my 20s was like musical chairs. Everybody was running around and having fun, but then sometime around 30 it was like the music turned off and everybody started sitting down.
    I didn’t want to be the only one left standing up, so sometimes I think I married my husband because he was the closest chair to me at 30." Where are the twenty somethings here? Do not do that. Okay, make no mistake, the stakes are very high. When a lot has been pushed to your 30s, there is enormous thirty something pressure to jump-start a career, pick a city, and have two or three kids in a much shorter period of time.
    Many of these things are incompatible, simply harder and more stressful to do all at once in our 30s. The midlife crisis in the 21st century isn’t buying a red sports car. It’s realizing you can’t have that career you now want. It’s realizing you can’t have that child you now want. Too many thirtysomethings and fortysomethings look at themselves, and at me, sitting across the room, and say about their 20s, "What was I doing? What was I thinking?"
Questions 16 to 18 are based on the recording you have just heard.
16. What did Leonard Bernstein say about achieving great things?
17. What do the twenty somethings usually do?
18. What is the midlife crisis in the 21st century according to the speaker?