Answer: A, C, D
r is proportional to n2/Z: ratio = (4/2)/1 = 2. v is proportional to Z/n: ratio = (2/2)/1 = 1, so speed is the same. T = 2 pi r/v is proportional to n3/Z2: ratio = (8/4)/1 = 2. E is proportional to Z2/n2: (4/4) = 1, so the energies are equal.