Answer (3) is the most correct, although (2) is not to be ignored. (3) states the most abundant isotope Ti's average mass, which is certainly true. (2) is the total mass of all protons, neutrons, and electrons in an atom of Ti, which is true but has to be more specific in order to pinpoint exactly the 47.88 amu. (4) is incorrect because it is not of all the naturally occurring isotopes of Ti. (1) is incorrect because they forgot electrons.
