Pl
which groups of items all contain a transparent part with at least one curved surface to refract light?

Hello @Lucysrv18,

How are you doing? Immediately I can say that answer choice D. is not the answer as a window pane noes not have a curved surface. Also I can say that answer choice B. is out as safety goggles do not have a curved surface. 

So your answer is either A. or B. and when you look good you see something in A. I have experience underwater, and I am constantly using Diving Masks. If there is one thing i can assure you about it, its that it does not refract light. The point of the mask is just so water does not enter your pupil. Therefore, B is your answer. An Owl's eye reflects light and contains a "lens" just like a human. Smart Phones have lenses to take photos, and magnifying glasses have lenses to see things closer. 

B. is your answer! :)

Thank you,
Darian D.

Use a magnet to separate iron, evaporate water, i'm not sure how to separate the other two i'm sorry but good luck

Hbr dissociates to form h+ and br-ca(oh)2 dissociates to form ca2+ and 2oh-the h+ and oh- react to form waterassuming the reactants are dissolved in water, the net reaction is h+ + oh- —> h2oif you’re asked to show all components of the reaction, the complete reaction is 2hbr + ca(oh)2 —> cabr2 + 2h2o