I'm reading an article by DWT (https://www.dailywritingtips.com/because-of-and-due-to/), and I'm unable to diagram I missed the class because of the rain. Do I treat because of as the head of adverbial prepositional phrase modifying missed and attach the rain to it as the OoP?
Because of is a preposition, and as any preposition it forms a prepositional phrase (here: an adverbial modifier).
According to Oxford Living Dictionary:
: On account of; by reason of.
‘they moved here because of the baby’
on account of, as a result of, as a consequence of, owing to, by reason of, on grounds of, by dint of, due to