听力原文：
Conversation One

W: One of the most interesting experiments with dolphins must be one done by Doctor Jarvis Bastian. What he tried to do was to teach a male dolphin called Bass and a female called Doris to communicate with each other across a solid barrier.
M: So how did he do it exactly?
W: Well, first of all, he kept the two dolphins together in the same tank and taught them to press levers whenever they saw a light. The levers were fitted to the side of the tank next to each other. If the light flashed on and off several times, the dolphins were supposed to press the left-hand lever followed by the right-hand one. If the light was kept steady, the dolphins were supposed to press the levers in reverse order. Whenever they responded correctly, they were rewarded with fish.
M: Sounds terribly complicated.
W: Well, that was the first stage. In the second stage, Doctor Bastian separated the dolphins into two tanks. They could still hear one another, but they couldn't actually see each other.
The levers and the light were set up in exactly the same way except that this time it was only Doris who could see the light indicating which lever to press first. But in order to get their fish, both dolphins had to press the levers in the correct order. This meant of course that Doris had to tell Bass whether it was a flashing light or whether it was a steady light.
M: So did it work?
W: Well, amazingly enough, the dolphins achieved a 100 % success rate.
Questions 19 to 21 are based on the conversation you have just heard.

Q19：What is the purpose of Doctor Jarvis Bastian's experiment?

细节题。对话开始部分女士就说Doctor Jarvis Bastian的实验是想要教一只叫Bass的雄海豚和一只叫Doris的雌海豚通过一道屏障和对方进行交流。故选C。

听力原文：
Conversation One

W: One of the most interesting experiments with dolphins must be one done by Doctor Jarvis Bastian. What he tried to do was to teach a male dolphin called Bass and a female called Doris to communicate with each other across a solid barrier.
M: So how did he do it exactly?
W: Well, first of all, he kept the two dolphins together in the same tank and taught them to press levers whenever they saw a light. The levers were fitted to the side of the tank next to each other. If the light flashed on and off several times, the dolphins were supposed to press the left-hand lever followed by the right-hand one. If the light was kept steady, the dolphins were supposed to press the levers in reverse order. Whenever they responded correctly, they were rewarded with fish.
M: Sounds terribly complicated.
W: Well, that was the first stage. In the second stage, Doctor Bastian separated the dolphins into two tanks. They could still hear one another, but they couldn't actually see each other.
The levers and the light were set up in exactly the same way except that this time it was only Doris who could see the light indicating which lever to press first. But in order to get their fish, both dolphins had to press the levers in the correct order. This meant of course that Doris had to tell Bass whether it was a flashing light or whether it was a steady light.
M: So did it work?
W: Well, amazingly enough, the dolphins achieved a 100 % success rate.
Questions 19 to 21 are based on the conversation you have just heard.

Q20：What were the dolphins supposed to do when they saw a steady light?

细节题。根据对话内容可知当灯闪烁几次之后，海豚应当先按左手边的控制杆，接着按右手边的控制杆，而当灯一直亮着时，海豚需要按照与之前倒着的顺序来安控制杆，即先按右手边的再按左手边的。故选B。

听力原文：
Conversation One

W: One of the most interesting experiments with dolphins must be one done by Doctor Jarvis Bastian. What he tried to do was to teach a male dolphin called Bass and a female called Doris to communicate with each other across a solid barrier.
M: So how did he do it exactly?
W: Well, first of all, he kept the two dolphins together in the same tank and taught them to press levers whenever they saw a light. The levers were fitted to the side of the tank next to each other. If the light flashed on and off several times, the dolphins were supposed to press the left-hand lever followed by the right-hand one. If the light was kept steady, the dolphins were supposed to press the levers in reverse order. Whenever they responded correctly, they were rewarded with fish.
M: Sounds terribly complicated.
W: Well, that was the first stage. In the second stage, Doctor Bastian separated the dolphins into two tanks. They could still hear one another, but they couldn't actually see each other.
The levers and the light were set up in exactly the same way except that this time it was only Doris who could see the light indicating which lever to press first. But in order to get their fish, both dolphins had to press the levers in the correct order. This meant of course that Doris had to tell Bass whether it was a flashing light or whether it was a steady light.
M: So did it work?
W: Well, amazingly enough, the dolphins achieved a 100 % success rate.
Questions 19 to 21 are based on the conversation you have just heard.

Q21：How did the second stage of the experiment differ from the first stage?

细节题。在实验的第二个阶段，两只海豚被分别放置于不同的容器中，而灯和控制杆的位置几乎不变动，而且只有雌海豚可以看到灯的状态来决定需要先按哪个控制杆。即实验第二阶段和第一阶段的不同之处就在于只有一个海豚能够看到灯光。故选A。