Why doesn't the formation of the Grignard reagent start immediately upon the addition of 1-bromobutane to the magnesium turnings? Why does the reaction proceed very rapidly once it commences?
a) The reaction is slow due to steric hindrance.
b) The magnesium surface is coated with an oxide layer, which must be removed first.
c) The Grignard reagent is unstable at room temperature.
d) The reaction proceeds rapidly due to the high reactivity of magnesium with 1-bromobutane.