A、Small and lightweight. B、Solid and heavy. C、Bulky but weightless. D、Large but necessary. A事实细节题 男士描述这种净水器小而轻，便于携带。

M: I’ve just found the most useful device at that new outdoor store, a water purifier.
W: A water purifier! You want to carry even more equipment with you on our hiking trips?
M: If it is 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 a milkshake.
W: Really? That’s small.
M: It’s plastic and has a series of mineral and chemical filters that strain harmful microbes from water.
W: Yes, but how good a job can it do filtering the germs out of stagnant 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? Does it clean them out?
M: No, it doesn’t remove salt and chemicals. But these are really not major concerns when we’re out hiking and camping.
W: Hm... How long will a straw last?
M: For about 100 gallons. But don’t worry about measuring that large amount of water. There is a built- in safety feature. The mineral and chemical filters become clogged long before the limit is reached, and the straw then stops drawing water.
W: I think I’ll go and get one for my camping trip this weekend.