Da also exists as a main verb ('to give') in the language. In the serial construction, however, syntactic testing shows that da behaves like a preposition, except for one case: when its complement is extracted (e.g. fronting), the verb is stranded without a spelled-out trace, corresponding to the 3SG pronoun. In this respect, da behaves like a verb, since the few prepositions proper are stranded with a spelled-out trace (Hagemeijer 2000).
Source: Hagemeijer 2000: 100
Source: Hagemeijer 2000: 101