The right answer is C. +1 (for hydrogen).
The hydrogen atom can lose its single electron to give the H + ion, commonly referred to as the proton name. In fact, the atom which has lost its only electron is reduced to its nucleus, and in the case of the most abundant isotope 1H, this nucleus consists only of a proton. This name is not strictly correct if one takes into account the presence, although discrete (less than 0.02%), of the other isotopes. The name hydron is more general (we also say hydrogen ion, despite the possible confusion with the H- anion).
