If there are 3 bond pairs and one lone pair in the valence shell of central atom, then they must be separated by

In a molecule, if the central atom has ${\text{sp}}^3$  hybridization with 3 bond pairs (B.P) and 1 lone pair (L.P) electrons are present then the shape of molecule is Trigonal pyramidal instead of regular tetrahedron and the bond angle is $\text{107°48'}$. This is due to L.P and B.P electrons repulsions at the central atom