A．Sewage and industrial waste.
B．Oil pollution on the beach.
C．Oil discharged at sea when people cleaning oil tanks.
D．The oil that leaks out after ship collisions.

A．She couldn’t get admitted to a medical school.
B．She decided to further her education in Paris.
C．A serious eye infection stopped her quest.
D．It was difficult for her to start medical practice in the United States.