Which two conditions explain why special technology is required to study the deepest parts of the ocean? A. Uneven terrain on the ocean floor B. extremely high pressure C. thickness of ice on the ocean floor D. unusually high oxygen levels

they both have a y in them

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.

c (diamond),

sio2 (quartz)