Unfortunately, this is a poorly asked question and none of the answers are truly right. The closest one to correct is C, although this can’t be deduced from this experiment alone.
A is not correct - other elements can produce spectral lines (and even if they couldn’t, this experiment wouldn’t be able to determine that).
B is not correct - elements produce different spectral lines based on the number of protons that are in the nucleus, amongst a number of other things (again, this wouldn’t be able to be determined from this experiment alone).
D is also not correct, hydrogen is a gas at room temperature and the production of the spectral lines comes from ionizing the gas itself.
Hope this helps!
