**(A) 10**^{6} N m^{-2}

d = 6 mm = 0.006 m, l = 42 cm = 0.42 m,

∆l = 20 cm = 0.2 m, m = 0.02 kg, v = 20 m/s

Energy stored in the catapult,

Energy stored in the catapult gives the kinetic energy to the stone.

= 3 × 10^{6} N/m^{2}

∴ Y is closest to 10^{6 }N m^{-2}