a.trigonal pyramidal,b.octahedral c.trigonal planar, d. tetrahedral.

How many electron clouds surround the Nitrogen atom? What hybridization does that require? What shape does it demand?

Trigonal pyramidal

Unfortunately no. The ammonium ion has 4 bonded pairs of electrons, 3 of them being shared with hydrogen atoms while the last is a dative covalent bond (where the two electrons are from the lone pair of electrons of nitrogen and hydrogen doesn't provide any electron) with a positively charged hydrogen ion.

Hence, the shape is tetrahedral.

The bonded ATOMS give the molecular shape. (They ALL usually have four electron clouds to give them their octet.) How will the four hydrogen atoms be arranged around the nitrogen atom? In the ammonium ion, all four N-H bonds are identical, regardless of the source of the electrons. There is no longer a hydrogen ion.
Unknown008 is absolutely correct, NH4+ has a tetrahedral shape, just like CH4. Got it?

Thanks a bunch