2-Fluorobutane is heated with $\mathrm{NaOEt}$ in ethanol. Unlike 2-bromobutane, the major alkene is but-1-ene. This is best explained by:

1. Afluoride is a poor leaving group, so the transition state has carbanion character and favours removal of the more acidic, less hindered primary hydrogen
2. Bfluoride is an excellent leaving group, giving a very early transition state with no regioselectivity
3. Cfluorine is highly electronegative so the reaction goes by E1 with a stable carbocation
4. Dthe more substituted alkene but-2-ene is much less stable than but-1-ene