Arrange the following alkyl halides in order of dehydrohalgenation, `C_2H_5I` , C_2H_5Cl` , C_2H_5Br` , C_2H_5F`
A. `C_2H_5FgtC_2H_5ClgtC_2H_5BrgtC_2H_5I`
B. `C_2H_5IgtC_2H_5BrgtC_2H_5ClgtC_2H_5F`
C. `C_2H_5IgtC_2H_5ClgtC_2H_5BrgtC_2H_5F`
D. `C_2H_5FgtC_2H_5IgtC_2H_5BrgtC_2H_5Cl`