Answer
A plasma membrane receptor would be expected since NGF is water-soluble and receptors for those kinds of signals are usually found in the plasma membrane due to their inability to readily move through the membrane to intracellular receptore.
Work Step by Step
Review the concept in the textbook and recall how different molecule types interact with lipid membranes-- you will see that there are water-soluble signals with plasma membrane receptor, and why this may be the case. More hydrophobic signals such as steroids may move through the membrane to utilize intracellular receptors.