Which of the following equations can be used to calculate poh?

There is not any options, but to calculate the pOH, you would use the equation

pOH = -log [OH-]
pH = -log [H+]

to check and see if you’re correct, use the values of both pOH and pH (pH + pOH) and see if it equals 14. if it does, then you’re right. if it doesn’t, you have probably made a minor mistake. have a great day!

It reflects sunlight.  It's a physical barrier (in comparison to some sunscreens which are chemical blocks).  Sunlight is mostly white light and zinc oxide reflects white light