Mapping of the ocean floor

Correct answer: A. Sound-wave-based sonar technique

Explanation: The governing concept is bathymetric surveying, or the measurement and mapping of underwater depth and relief. Sonar sends sound pulses through the water and records the time taken for their echoes to return from the seabed. With the speed of sound in water and the measured return time, instruments estimate depth; repeated measurements from a vessel or other platform are then used to construct a map of the ocean floor. Option A is correct. Hand measurement cannot cover the vast and inaccessible seabed, birds cannot measure underwater depth, and plant roots are not a surveying instrument. Modern multibeam sonar can collect many depth readings across a wide strip, making mapping more accurate and efficient.

Correct answer: A. Bathymetry

Explanation: The governing concept is the scientific measurement and description of underwater depth and relief. Bathymetry is the branch of marine surveying concerned with determining water depth and representing the shape of the seabed, often by using sonar, echo sounding, satellite observations, and other instruments. Option A is correct because it directly names the study of ocean-floor depth. Seismography records and analyzes earthquake waves, although seismic methods can sometimes support studies of the seabed or crust. Climatology examines long-term atmospheric and climate patterns, while pedology studies soils. The key distinction is that bathymetry focuses specifically on underwater depth and bottom topography, not earthquakes, climate, or soil.

Correct answer: A. Bathymetric map

Explanation: The governing concept is bathymetry, the measurement and mapping of underwater depth and relief. A bathymetric map represents the shape of the sea floor by showing depth values, depth zones or contour lines called isobaths. It can therefore distinguish shallow shelves, steep slopes, deep plains and trenches, making option A correct. A political map shows administrative boundaries, not underwater elevation. A rainfall map represents the spatial distribution of precipitation, while a vegetation map shows plant cover or vegetation regions. These maps may be useful for other geographical questions, but they cannot provide the required systematic information about ocean depth. The map must match the variable being measured: bathymetry matches depth.

Correct answer: A. Bathymetric map

Explanation: The governing concept is bathymetric mapping, which is the underwater equivalent of topographic mapping. A bathymetric map records variations in the depth and shape of the sea floor, including shelves, slopes, ridges, plains, trenches and underwater mountains. Depths may be represented with contour lines, colour bands or numerical soundings. Thus, option A is correct: a bathymetric map shows the relief of the ocean floor through its heights and depths. A political map shows boundaries, a soil map shows soil distribution, and a population map shows human concentration; none of these describes submarine elevation or depth.

Correct answer: A. Sea depth and floor shape

Explanation: Bathymetry is the measurement and representation of underwater depth and the shape of the sea floor. By using tools such as echo sounding, sonar and satellite-based measurements, scientists estimate water depth and prepare charts showing submarine relief. Bathymetric maps can reveal shelves, slopes, basins, ridges, seamounts, plains and trenches. Therefore option A is correct because it combines the two essential outputs: depth and bottom configuration. Sea-breeze direction belongs to atmospheric or coastal meteorology, cloud height is an atmospheric observation, and coastal-city population is a demographic statistic. None of those describes bathymetry.