The Balmer series for the H-atom can be observed:
 

a. if we measure the frequencies of light emitted when an excited atom falls to the ground state
b. if we measure the frequencies of light emitted due to transitions between excited states and the first excited state
c. in any transition in a H-atom
d. as a sequence of frequencies with the higher frequencies getting closely packed

1. (b, c)

2. (a, c)

3. (b, d)

4. (c, d)

(3) Hint: Use the concept of transitions in the Balmer series.
Balmer series for the H-atom can be observed if we measure the frequencies of light emitted due to transitions between higher excited states and the first excited state and as a sequence of frequencies with the higher frequencies getting closely packed.