Which of the following statements about a proton is correct?

A proton is positively charged and its mass is taken as one unit. In atomic physics, a proton's mass is approximately 1.67x10^-27 kg, which is taken as one atomic mass unit (amu). An electron is a stable, negatively charged fundamental subatomic particle that orbits the nucleus, possessing a mass of roughly 9.11x10^-31 kg. A neutron is a fundamental subatomic particle found in the nucleus of every atom (except hydrogen), possessing no net electric charge and a mass slightly greater than a proton.