Which of the following are characteristics of rogue waves?

a. They have been documented as high as 34 meters by ships in the ocean.
b. They are figments of the imagination of sailors.
c. They may form when wind-driven waves encounter strong water currents.
d. They are not affected by the shape of the seafloor.
e. They may form when wind-driven waves converge from two different directions.
f. They are half as high as the typical highest waves in a region.