If a action verb is followed directly by a direct (DO) and indirect object (IO), then it is a ditransitive verb.

*Note that all DT verbs can go through the transformation below:

e.g., I wrote [him] [a letter].

NP: IO + NP: DO

I wrote [a letter] [to him].

NP: DO + PP: Advl. (opt.)

The DO is fronted and the IO is placed after the preposition 'to'. In the transformed sentence, the verb 'wrote' turned into a MT verb.