Answer
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Work Step by Step
The first reaction is impossible.
Conservation of charge is violated: $1+1 \neq 1 + (-1)$.
Conservation of baryon number is violated: $1 +1\neq 1 + (-1)$.
The second reaction is impossible.
Conservation of charge is violated: $1+1 \neq 1 + 1 + (-1)$.
Conservation of baryon number is violated: $1 +1\neq 1 + 1 + (-1)$.
The third reaction is possible. Quantities are conserved.
The fourth reaction is impossible.
Conservation of baryon number is violated: $1 +1\neq 1 + 0 + 0 +(-1)$.
Conservation of lepton number is violated: $0 +0\neq 0 + (-1) +(-1) + 0$.
