声音与人的生活息息相关，为了认识声音，某实践活动小组设计了以下实验对声音进行了探究．

实验一：使正在发声的音叉接触水面溅起水花．

实验二：用细线把一个小铃铛悬挂在软木塞的下端，并置入烧瓶中，摇一摇瓶子，会听到清晰的“叮当”声．然后取下软木塞点燃酒精棉球放入瓶中，待火熄灭后，迅速塞紧软木塞，再摇瓶子，听到瓶里的响声比原来小很多．

实验三：支起自行车，一手转动自行车的脚踏板，另一只手则拿一硬纸片并让纸片一头伸进自行车后轮的辐条中，随着车轮转速的加快，纸片发出的声音会越来越尖．

（1）以上三个实验中，实验 ____表明发声体在振动．

（2）实验二表明： ____；

（3）实验三表明： ____

条件p：x＞1，y＞1，条件q：x+y＞2，xy＞1，则条件p是条件q的（　　）

D

    A bag is useful and the word "bag" is useful, too. Here is an interesting phrase, "to let the cat out of the bag". In meaning it is the same as "to tell the secret". And there is an old interesting story about it. Long ago, when farmers wanted to sell chickens at the market, they would usually throw the chickens in cloth bags. But cats were cheaper than chickens at that time, so many farmers would put cats into the cloth bags but not chickens.

    One day, a woman asked a man for a chicken. The man gave her a cloth bag in which there was a cat. The woman begged to see the chicken. When the man opened the cloth bag, a big black cat ran out. Not a chicken! The man's secret was out and everyone knew it.

    Now when we say someone gives away a secret, we say "he lets the cat out of the bag". And that is the story where the interesting phrase came from.

宋朝武将受到多方面的牵制，而文臣担任中央和地方要职，体现了宋朝的政策是（  ）