Here it says which of the following electron emissions corresponds to the bomber series of lines in the spectrum of a hydrogen atom. Right here it doesn't matter that it's dealing with a hydrogen atom. What's important is that we're dealing with a bomber series. Remember, in a bomber series we go from a higher shell number, which we can call Infinity, and our final destination is to land on shell #2, so we're landing on n=2.
So all we have to do is look and see which option shows us going from a higher shell number and stopping at shell #2 that represents A bomber series. So if we take a look at all the options, the only one that has a higher shell number ending at shell #2 will be option B.
In B we start off with the electron existing in shell #5 and then emits energy or light and drops back down to show #2. This represents A bomber series for an emission line Spectra.