We know, according to Bohr’s Model, the energy ∆E released, when electrons move from n₂ energy level to n₁ energy level is given by,

Now, the photons having energies can be due to the following transitions:

From n=3 to n=1:

From n=3 to n=2:

From n=2 to n=1:

Now, an excited electron always comes to its ground state. Since there is only one electron in hydrogen atom, it can make transitions from n=3 to n=1 directly or from n=3 to n=2 and then finally from n=2 to n=1.

This is not possible for a single atom as only one transition is allowed. So option (a) is wrong.

This is possible for two atoms where one atom makes n=3 to n=1 transition and the other makes n=3 to n=2 and then to n=1 transitions.

This is also possible for three atoms where all the three atoms make three different transitions.

Here, only one option is correct. So among (b), (c) and (d) options, we choose (d) as it includes all the cases.

Hence, option (d) is the correct answer.