First of all, "groups" don't give NMR signals, nucleus do.
I guess, since you are starting, you talk about 1H NMR, so those arrows shouldn't point to carbons, but to hydrogens.. (In case you are learning 13C NMR, it would be kinda the same reasoning)
That being said, the more DESHIELDED (electron density substracted by any other atom or functional group) a nucleus is, the more chemical shift it will show (i.e, it will show up more "to the left").
If you know that, you just need to tell which compound has a more electron-withdrawing "thing" near the nucleus you are studying (in the first compoud all H are the same and it the second one there are 2 kinds).