Which of the following combinations of hybridization and molecular geometry is possible?
1. sp^3: trapezoidal
2. sp^3: trigonal pyramidal
3. sp^3: octahedral
4. sp^2: tetrahedral
5. sp^2: linear
6. s(p^3)d : octahedral
7. sp^3: trigonal planar
8. s(p^3)d : tetrahedral