B. Keywords.

force of attraction, spark, penetrate, electromagnetic waves, fungus, resistance to movement, energy efficient.
Vocabulary.

opaque, ruby, ferment, ball bearing, lubricating oil, Light Amplification by the Simulated Emission of Radiation (LASER).
You're going to hear 7 short spoken abstracts.As you listen, pay special attention to the subjects that the speakers are talking about, and their tones of voice. The first one has been done for you as a example.
1. Yes, you see. It's the force attraction between any two objects.
And the strength of the force depends on the mass of objects and the distance between them.
The most obvious effect is the way objects on the surface of the Earth are attracted towards the center of the Earth.
2. As it comes down, it goes relatively slowly, 100 to 1000 miles per hour, and you can't see it.
But the return stroke goes up from the Earth to the cloud and it goes at over 87,000 miles per hour and that's the one you can see.
You see, the one that goes back up. It's really just a very large powerful spark.
The distance in miles you are away from it is the time in seconds between it and the sound you hear.
3. Well, they were first discovered in 1895, and they can penetrate matter that is opaque to light.
Some matter is more transparent to them than others, which means you can see inside somebody.
They are actually quite dangerous and people who work with them wear special protective clothing.
4. Ordinary light consists of electromagnetic waves of different frequencies and phases.
This is a bundle of waves of the same frequency and phase.
You can create the beams from a ruby rod or a tube of carbon dioxide that's simulated with flashes of ordinary light.
The word is an acronym for Light Amplification by the stimulated emission of radiation. Now does anybody...
5. They are all types of fungus.
There are many different kinds of them, but the best known are the ones used in cooking and brewing.
When they are mixed with sugar, they cause the sugar to ferment and two things happen.
First, carbon dioxide is given off and Second, alcohol is formed,
when the proportion reaches 12%, it's all killed off naturally...
6. ...in contact with each other, there's a resistance to movement between them.
The main reason why we use ball bearing and lubricating oil is to counteract this.
The main reason why rubber is used in tyres and shoes is to increase the effect of it...
7. ...No, it's the process whereby materials are used again.
Normally, it's cheaper to do this because it's more energy efficient.
On the other hand, one material that's hard to deal with in this way is plastic, there are so many types that it's very difficult to separate...