( A ) stronger σ bond between B and F in BF3 as compared to that between C and F in CF4
( B ) smaller size of B-atom as compared to that of C-atom
( C ) lower degree of pπ−pπ interaction between B and F in BF3 than that between C and F in CF4.
( D ) significant pπ−pπ interaction between B and F in BF3 whereas there is no possibility of such interaction between C and F in CF4