It is also not shown by giving just one structure. Also, it is important to state which meaning is associated with which of the two structures. There was substantial variability in how well this was done. You should review this material again if you are unsure of how to use the test - it allows you to determine what must go inside the smallest VP in a sentence. This is something that the Trees program always does for you automatically, but that is not much help when you're figuring out sentence structures without the aid of the program.
Arguments are inside the smallest VP, and are sisters of a V node.
VP-modifiers are outside the smallest VP, and are sisters of a VP node. Although PPs are often modifiers, with some verbs they show the behavior of arguments. There were instances of argument PPs in the homework exercise. 0.5 points for each example, up to a maximum of 1 point. To count as a relevant example, your ungrammatical sentence needed to be formally incorrect, not just semantically weird.