M: I've just found the most useful device at that new outdoor store,a water purifier.
W: A water purifier?(1)_______________________.
M: If it's lightweight and saves work,yes.And this one fits that description.
W: Really.I bet it takes up a lot of room.
M: Not at all.It's a straw,much like the ones you use to drink a soda or milk shake.
W: Really? That is small?
M: Yeah, (2)_______________________.
W: Yes,but how good a job can it do filtering the germs out of motionless pond water,or water from lakes and streams?
M: It's fantastic. It makes the water entirely germ free.
W: But what about salt or chemical pollutants that might be in the water?Does it clean those out?
M: No,(3)_______________________.
W: Hmm,how long will a straw last?
M: For about one hundred gallons but don't worry about measuring that large amount of water.There is a built-in safety feature.
W: I think I'll get one for my camping trip this weekend.It'll sure be carrying a lot of water or having to boil it at the camp site.
