JEE Advanced 2013 · Paper 2, Chemistry question 22

Balance A and Z. $^9_4$Be + X → $^8_4$Be + Y needs X and Y to have the same Z, with Y one nucleon heavier.

• (γ, n): $9+0=8+1$, $4+0=4+0$ ✓
• (p, D): $9+1=8+2$, $4+1=4+1$ ✓
• (n, D): Z: $4+0\ne4+1$ ✗
• (γ, p): Z: $4\ne4+1$ ✗

(A), (B)