Answer : 1. "Positron"
Explanation :

The positron is the antiparticle to the electron. The positron has the same rest mass (m₀) as the electron but opposite charge, one positive elementary charge. In condensed matter, each positron annihilates with an electron yielding γ-rays in a very short time (10⁻¹⁰–10⁻⁹ s).