在实数范围内,下列各式一定不成立的有(    )
(1)$\sqrt{a^2+1}$=0; (2)$\sqrt{a-1}$+a=0; (3)$\sqrt{2a-3}$+$\sqrt{3-2a}$=0;(4)$\frac{1}{a-2}$=0.

A

    Nick, 13, is tall and strong. He is good at running. Two weeks ago a new student came. His name is David. He is thin and short. He plays soccer well, and he can run very fast. Larry told Nick about it. Of course, Nick did not believe it.

    “Why not have a race with him?” said Larry.

    “Good idea!” said Nick. “I'll have a race with him after school.”

    After school, Nick went to the playground. He did some warm-up exercises for half an hour, and got ready for the race. He was sure that he could win it. Larry had to take part in a club activity that afternoon, so he could not watch the race between Nick and David.

    That evening Larry went to see Nick. They began to talk about the afternoon race. Nick's grandmother heard them in the next room. She came in and asked, “Which place?”

    “The second place,” answered Nick.

    His grandmother was very happy to hear that, and asked, “Which place did David win, then?”

    “The last but one.”