The correct option is C H−
Using the rules of nomenclature, we see that the complex is an anion since the name ends with an -ate.
Tetrahydro refers to 4 hydrogens attached to the Al(III) ion. Remember hydro is hydrogen, hydrato is water! Do not get confused between the two.
Lithium always carries a charge of +1 so the compound looks like this:
The compound would be Li[AlH4]. Clearly, the ion [AlH4]− is the complex we are interested in.
So far so good?
Great!
Since Al(III) ion would have a +3 charge, the charge on the hydrogen would have to be:
3+4×hydro=−1
∴hydro=−1
Hence the ion in question is H− or the hydride ion.