Manyofthesoundingsshownonthechartare______inadequate

Many of the soundings shown on the chart are______inadequate and often very poor surveys ．Undue reliance should not be placed upon them．

A.drived from

B.derived by

C.derived from

D.drived by

正确答案：C
海图上许多测深数据源于不充分并且很早以前的测量不应过于信任这些数据