[originaltext] I recently turned fifty, which is young for a tree, midlife f

I recently turned fifty, which is young for a tree, midlife for an elephant, and ancient for a sportsman. Fifty is a nice number for the states in the US or for a national speed limit but it is not a number that I was prepared to have hung on me. Fifty is supposed to be my father’s age, but now I am stuck with this number and everything it means.
    A few days ago, a friend tried to cheer me up by saying, "Fifty is what forty used to be." He had made an inspirational point. Am I over the hill? People keep telling me that the hill has been moved, and I keep telling them that the high-jump bar has dropped from the six feet I once easily cleared to the four feet that is impossible for me now.
    "You are not getting older, you are getting better," says Dr. Joyce Brothers. This, however, is the kind of doctor who inspires a second opinion.
    And so as I approach the day when I cannot even jump over the tennis net, I am moved to share some thoughts on aging with you. I am moved to show how aging feels for me physically and mentally. Getting older, of course, is obviously a better change than the one that brings you eulogies. In fact, a poet named Robert Browning considered it the best change of all:
    Grow old along with me!
    The best is yet to be.
    Whether or not Browning was right, most of my first fifty years have been golden ones, so I will settle for what is ahead being as good as what has gone by. I find myself moving toward what is ahead with a curious blend of both fighting and accepting my aging, hoping that the philosopher was right when he said, "Old is always fifteen years from now."
Questions 16 to 18 are based on the passage you have just heard.
16. What does the speaker seem to tell us in the beginning of the passage?
17. How does the speaker consider his fifty years of life?
18. What can we infer from the passage?