The geometry of ammonia molecule can be best described as
A. Nitrogen at one vertex of a regular tetrahedron, the other three vertices being occupeid by the three hydrogen
B. Nitrogen at the centre of the tetrahedron, three of the vertices being occupied by three hydrogens
C. Nitrogen at the centre of an equilateral triangle , three corners being occupeid by three hydrogens
D. Nitrogen at the junction of a T, three open ends being occupied by three hydrogens