Thomas Edison worked ______ hours a day so he called himself a "two-shift man".

A．Several weeks.
B．Several months.
C．A few days.
D．Several hours.

A．From the top to the bottom, the water falls 3,200 feet.
B．These falls are more than 1,000 feet higher than any other falls in the world.
C．From the top to the bottom, the water falls a bit less than 3,200 feet.
D．Both A and B.