Incorrect order between following compounds is/are:
a. O(CH3)2<O(SiH3)2 : number of sp3 -hybrid atoms
b. O(CH3)2<O(SiH3)2 : Bond angle w.r.t. common atom
c. O(CH3)2<O(SiH3)2 : % s -character of hybrid orbital on central atom
d. O(CH3)2<O(SiH3)2 : reactivity towards Lewis acid