The correct option is B 4→2
For the first Lyman transition for hydrogen,
1λ=RZ2(1n21−1n22)=R12(112−122)=3R4
Since, wavelength of the radiation emitted in electronic transition in He+ is the same as for hydrogen,
1λHe+=R.22(1n21−1n22)=3R4
Hence, n1 and n2 have to be 2 and 4 respectively as,
1λ=4R(122−142)=3R4