(a) large water bodies
(b) heavenly bodies
(c) mountainous region
(d) canal system
Ans (a) : large water bodies

Expalanation :-
Marine or hydrographic survey – Marine or hydrographic survey deals with large bodies of water for purpose of navigation, water supply, harbor works or for the determination of mean sea level. The work consists in measurement of discharge of streams, making topographic survey of shores and banks. Taking and locating soundings to determine the depth of water and observing the fluctuations of the ocean tide.