### Correct Answer: D An antiparticle is a subatomic particle with the same mass as its corresponding ordinary particle but with the opposite electric charge and other quantum numbers. The antiproton is the antiparticle of the proton. * **Mass:** The mass of an antiparticle is identical to the mass of its particle counterpart. Since the proton has a mass denoted by *m*_p, the antiproton must also have a mass of *m*_p. Mass is an intrinsic property of a particle and is a positive scalar quantity. * **Charge:** The electric charge of an antiparticle is equal in magnitude but opposite in sign to that of its corresponding particle. The proton has a charge of +e (the elementary charge). Therefore, the antiproton must have a charge of -e. Combining these two properties, the antiproton has a mass of *m*_p and a charge of -e. --- ### Incorrect Answer Explanations **A:** This option is incorrect because it proposes a negative mass (-*m*_p) and a positive charge (+e). Mass is a positive scalar quantity; negative mass is not a property of known antiparticles. Furthermore, the charge of an antiproton is opposite to that of a proton, so it should be negative, not positive. **B:** This option correctly identifies the charge of an antiproton as -e, but it incorrectly states the mass as -*m*_p. The mass of a particle and its antiparticle are identical and positive. Therefore, the mass of an antiproton is *m*_p, not -*m*_p. **C:** This option correctly identifies the mass as *m*_p but incorrectly states the charge as +e. These are the properties of a proton, not an antiproton. The defining electrical characteristic of an antiproton is its negative charge, which is opposite to the proton's positive charge.

11: Particle physics