15. please help

Use the following information to answer the next question Some wristwatch faces are coated with a layer of phosphor and filled with tritium gas. The spontaneous beta decay of the tritium (Hydrogen-3) causes the phosphor coating to glow. These types of watches glow continuously in the dark without previous exposure to a light source. 15. Which of the following equations shows the beta decay reaction that occurs in the wristwatches described above? O 17 20 9 10 O'A O 3 He + 2