[Ammar Qasim]

How could I know the hybridization type in such a question

[Hunter2]

Get the structure of each molecule by the rules of VESPR. Compare then the pairs.

http://en.wikipedia.org/wiki/VSEPR_theory

[Ammar Qasim]

I found that the structure of BH3 is similar to ClF3's. is (C) the right answer?

[sjb]

I found that the structure of BH3 is similar to ClF3's. is (C) the right answer?

What makes you sure there is just one right answer. I'm not sure that boron trifluoride and chlorine trifluoride have the same geometry - what is your VSEPR analysis?

[Ammar Qasim]

What makes you sure there is just one right answer. I'm not sure that boron trifluoride and chlorine trifluoride have the same geometry - what is your VSEPR analysis?

There must be only one right choice in this question. I tried that

So I think letter C would be the right answer

[Hunter2]

No, you have to consider the unpair electrons.

[sario]

I think that the right answer is B because the Nitrogen atom is sp3. In NH3 one sp3 orbital is occupied by two electrons, on the other hand in the ammonium ion all the four sp3 orbitals make a covalent bond with Hydrogen atoms.

[Hunter2]

Correct, but the TES should answer it.