Hey Dorsa, I’m sorry for the delay and thanks for the feedack!
I also marked D, but I dot know why the answer is E.
Hi! i found this explanation online:
probability having two ¹⁰B with mass of 26 = 0,2 * 0,2 = 0,04
probability of 1 ¹⁰B and 1 ¹¹B with mass of 27 = (O,2 * O,8) + (0,2 * 0,8) = 0,32
if you draw a probability tree diagram you see you could have two possibilities ¹⁰B ¹¹B or ¹¹B ¹⁰B
probability having two ¹¹B with mass of 28 = 0,8 * 0,8 = 0,64
so a ratio of 1:8:16