Hi Vanessa!
You're right -- this question is a bit tricky, but it comes down to what we mean by "drop in."
In the sentence, "Drop the money in the container," the verb is really drop and "in" is part of the prepositional phrase, "in the container."
This becomes especially confusing because if you use "drop off" such that "Drop off the money in the container," drop off is a phrasal verb, but notice the difference: drop off is the phrase for the verb and in is still part of the prepositional phrase.
Another way of thinking about this is that "drop in" as a phrasal verb only really means: "to visit." For example, "John dropped in on the way home." The phrasal verb is "dropped in" -- as if the verb itself is "drop in."
Phrasal verbs are nearly always together and won't be split: it will pretty much always be "drop in" together and the exceptions are very specific.
Feel free to respond to this response with any more specific questions! Good luck!!
