The distance between rivets in a row is known as the（）.

A.one engine and a steering oar
B.both engines at the same speed
C.one engine at a time
D.one engine running at reduced speed and controlling the vessel with the other

A.low and bare，but the land back of it is high and wooded
B.composed of low to medium rolling hills
C.well defined with rocky outcroppings
D.marked by high，barren hills

A.pitching
B.rolling
C.heaving
D.swaying