Answer
See the answer below.
Work Step by Step
a) O, oxygen is more electronegative than hydrogen and has a formal charge of -1
b) H, hydrogen is more electronegative so despite boron's formal charge being -1, the actual charge is distributed among the hydrogens.
c) The oxygens, they are more electronegative than carbon and the one making a single bond to it has a -1 formal charge. Since they display ressonance, the charge is distributed between them.
