Answer:
Cotton is a plant that needs a long frost-free period, a lot of heat and plenty of sunshine. It prefers warm and humid climate. Cotton seeds will have a small germination rate, if the soil temperature is below 60°F (15°C). During active growth, the ideal air temperature is 70 to 100°F (21-37°C)
A prepositional phrase consists of a preposition and its object. Therefore, the prepositional phrase is A, under the wooden bridge.
