A、they saw it was black. B、they believed in the supernatural. C、they wanted the inventor to be famous. B

BOB: Hi Julia.
JULIA: Hi Bob. Thought about the science project yet?
BOB: Which one? The presentations are scheduled for next month!
JULIA: The experiment that you and I are working on--to demonstrate density, buoyancy and thecompression of gases.
BOB: That’ll be complicated.
JULIA: Well, it’s not supposed to be. It’ll be part of the ’ Making Science Simple’ series that’s being showcasednext year. And we have to be ready to demonstrate by the end of next week.
BOB: Oh, well, ...simple...you say.
JULIA: Yes, not just the concept but the materials too. We have to use cheap, readily available, commonitems—expensive lab equipment is out of the question!
BOB: I remember something about using recycled or throw-away items if possible...Anything portable thatwe can bring into the lab.
JULIA: That’s right.
BOB: Well, any ideas for the project?
JULIA: What about the classic Cartesian diver?
BOB: Is that the same as a Cartesian devil? The invention named after the famous French physicist—RenéDescartes?
JULIA: Yes, a long time ago superstitious people labeled it that because they couldn’t comprehend thescientific principles it demonstrated; they thought it was black magic.
BOB: How shall we do it?
JULIA: By keeping it as simple, transparent and economical as possible.
BOB: So, to start with...?
JULIA: Open your pencil case and let’s have a look. Mum, you haven’t got any...
BOB: Any what?
JULIA: Paper clips.
BOB: Oh, there are lots of them in the bottom of my bag. They slip off my papers and collect in the bottom.Look, here’s half a dozen.
JULIA: But they’re all big metal ones—I want little ones—small, vinyl-covered multi-colored ones.
BOB: Oh, I’ve got one or two of them too.
JULIA: Great. And...if we look around, especially on the floor, we’re bound to find a few more. See? Here.
BOB: What else do we need?
JULIA: A small rubber band.
BOB: Well, I’ve got one of those in my pocket.
JULIA: No, not that kind. Let’s go and ask Tara.
BOB: Why?
JULIA: Those really small colored bands for making pony tails are ideal.
BOB: Hey, Tara?TARA:         Yes?
JULIA: Have you got any spare rubber bands like the ones you fasten your hair with?TARA:         Oh, heaps, a whole packet full--help yourselves.
BOB: Terrific....So far it hasn’t cost us anything. What now?
JULIA: Let’s go and rummage through the recycling bins beside Joe’s Mini-market.
BOB: What for?
JULIA: We want a 2-1itre plastic soft drink bottle with lid.
BOB: Hey, I draw the line at sorting through other people’s rubbish and we’re also not likely to find one witha lid.
JULIA: Well, go into the store and buy 2 liters of soft drink.
BOB: What flavor?
JULIA: It doesn’t matter what kind of drink you get, just make sure it comes in a clear P. E. T. bottle.
BOB: Where are you going?
JULIA: To the cafeteria behind the Resource Centre.
BOB: What for?
JULIA: I’m after some straws.
BOB: I can get them from the shop when I buy the drink.
JULIA: No, I’ve seen theirs. They’re the waxed paper ones. We need clear plastic and I know they’ve got themin the cafeteria. I’ll also see if I can get a tall plastic cup from there.
BOB: Good luck. Meet you back here in 5 minutes.
JULIA: Maybe longer because I want to go over to my locker and get a wire coat hanger.