Can someone tell me why this answer is correct?

in a nickel-cadmium dry cell, which of the following statements is true?

the cathode reaction is cd + 2oh- (arrow) cd(oh)2 + 2e-

the anode reaction is nio2 + h2o + 2e- (arrow) ni(oh)2 + 2oh-

the cathode reaction is cd + nio2 + 2h2o (arrow) cd(oh)2 + ni(oh)2.

I think you forgot to put the chosen and the correct answer along with your question. The statement "The anode reaction is Cd + 2OH- (arrow) Cd(OH)2 + 2e-" is the correct statement. This statement is valid and correct because Cadmium gets oxidized and releases two electrons. These electrons helps in the formation of Cd(OH)2. I hope the explanation has helped you.

Determine the  wavelength of light emitted when an electron  in an li2+ ion  makes a transition from an orbital with n  =  6 to an orbital with n  = 5.