When four atomic orbitals are mixed to form hybrid orbitals, how many hybrid orbitals are formed?

When four atomic orbitals are mixed to form hybrid orbitals, 4 x sp3 hybrid orbitals are formed.

Carbon's 2s and all three of its 3p orbitals hybridize to form four sp3 orbitals. These orbitals then bond with four hydrogen atoms through sp3-s orbital overlap, creating methane. 

Four

Explanation:

When atomic orbitals are combined, hybrid orbitals are formed. Hybrid orbitals exist only in covalent-bonded atoms and not in isolated atoms. The shapes and orientations of hybrids are different from that of atomic orbitals. The number of hybrid orbitals is same as the number of atomic orbitals that combined to form atomic orbitals. Thus, when 4 atomic orbitals are mixed then 4 hybrid orbitals are formed.

real, smaller and upside-down.   so the answer should be b.