I did not call to make my airline reservation, but I ____.

books，especially 21 on science．He had curious mind and always wanted to prove for himself 22 he read． 23 day，when he was sitting by an open window，it seemed that a thousand 24 filled his ears．“Where are they all 25 ？”he asked himself．“And where will they go？ What happens to all the words that people say？Do they 26 in the air around the earth， 27 waiting for someone to pick them up？” At once Marconi went to work．Sounds cal3 be made t0 28 ，he thought，if they are given a push by electricity．If I call push a piece of wood across the waves of water．I can also 29 sounds through the air waves by electrical power． A few weeks 30 he called his mother and father up to his workroom for a 31 .He touched a little machine，and two floors below there was the sound of a buzz(嗡嗡声)．“How did you do it？”they asked．“Your machine is 32 far from the sound．” “That’s right，”he said happily．“I have just found a 33 to carry sound without wires．’’ Although Marconi’S father did not think the wireless sound would 34 be important，he gave his son some money to 35 his work．“Father，with this money I am going to send messages round the world one day．’’

A.that

B.those

C.ones

D.one