No one can walk the wire in the air without a bit of fear unless ______ very young.

No one can walk the wire in the air without a bit of fear unless ______ very young.

No one can walk the wire in the air without a bit of fear unless ______ very young.

1. A.
   having trained
2. B.
   trained
3. C.
   to be trained
4. D.
   being trained

阅读下面短文, 掌握其大意, 然后从1-25各题所给的四个选项中, 选出一个最佳答案。

　　　　     One day two workers were installing (装设) electrical wires in the house. While they were working they 1 a problem: they had to put a 2 wire through a long 3 pipe. The pipe was about 10 metres long and only about 4 centimeters wide. 4 this pipe wasn't straight. It has several 5 in it, which made it rather 6 to pass the wire through the pipe.

　　     After thinking for some time, one of them, Frank, had 7. He told　　 his 8, Harry, that he was going to get what he needed. 9, Harry was a　　 little surprised.

　　    Thirty minutes later Frank 10 with two small white mice. He explained to Harry, "Hold this one very carefully, OK? Now 11 to that end of the pipe." Harry did so.

　　     Frank held the other mouse, a 12 mouse, at 13 end of the pipe.　　 Then Frank 14 the wire around the mouse's neck, and spoke to Harry,　　 "Now, very 15 pressed the mouse." Harry did 16 he was told. He　　 pressed lightly on the mouse. The mouse 17 a soft sound.　　 When the male mouse heard the sound, he began to 18 out of Frank's hand into the pipe toward 19. Of course, the male mouse was 20 the wire. Frank 21 the other end of the wire in his hand.　　 22 a few seconds the male mouse came out of the end of the pipe where the 23 was. The 24 had been solved; the wire was 25 through the long pipe.