What is the typical appearance of a fully formed Tetraneura ulmi gall on an elm tree leaf?

A. A pale yellow patch with irregular lumpy projections on the top surface of the leaf
B. A stalked, club-like smooth pouch on the leaves of elm trees
C. A stalked, club-like pouch with a hairy opening on the top surface of the leaf
D. A hairy patch with smooth projections on the underside of the leaf
Answer: 