Before the 20th century, the measuring of the depth of the sea was

• A、inaccurate

• B、unknown

• C、uninteresting

• D、impossible

The third paragraph is mainly about

• A、the elements in the sea

• B、the weather on the sea

• C、the studies of the sea

• D、the sound under the sea

A. wealthy

B. short

C. learn

D. consisted

E. only

F. already

G price

H. made

I. large

J. fight

K. fortune

L. worth