Which of the following solutions bathing a red blood cell would be considered isotonic?

Which of the following solutions bathing a red blood cell would be considered isotonic?
a solution containing 300 mM NaCl
a solution containing 150 mM glucose
a solution containing 400 mOsm non-permeating solute
a solution containing 200 mOsm NaCl
a solution containing 100 mM MgCl2

I think that it is one of the ones containing NaCl but I don't understand what the measurements are. Can anyone help please?!

1 answer

A solution containing 100 mM MgCl2