Noun

However, what is of particular interest to us here is
the fact that the presence of the Complementiser' ''whether'' in (37) (b) above
excludes the possibility of having an inverted Auxiliary in pre-subject posi-
tion, as we see from the ungrammaticality of (38) below:
(38)      *John wondered ''whether would he get a degree''
Why should this be? The answer we propose here is that this is because both
'''Complementisers''' and inverted Auxiliaries occupy the pre-subject C position:
hence, when (as in (38) above) the C position is already filled by the '''Comple-
mentiser ''whether , inversion of the Auxiliary is not possible, on the assumption
that once a given position is filled by one constituent, it cannot be filled by
another (i.e. we can only have one constituent occupying any given position).