" sends a radio signal from the bottom of the ship to the sea-bed, from where it is reflected.
A.The marine sextant
B.The chronometer
C.The echo sounder
D.The radar
正确答案是C
" sends a radio signal from the bottom of the ship to the sea-bed, from where it is reflected.
A.The marine sextant
B.The chronometer
C.The echo sounder
D.The radar
正确答案是C