Most of Earth' s surface is ocean. The ocean floor is inaccessible for extensive research without equipment of greater technological sophistication than is currently available. It must ttherefore be true that scientists know less about the ocean floor environment than about almost any other environment on Earth. Which of the following, if true, provides the most support for the conclusion? ['Strong water currents circulate on the ocean floor, but the general pattern of their movement is not so well understood as is the pattern of air currents that circulate over land.', 'Many mountain ranges lie entirely beneath the ocean surface, yet new underwater surveying equipment has produced three-dimensional charts of them that are as accurate as those available for mountain ranges on land.', 'Very few people have seen detailed maps of extended regions of the ocean floor, even though such maps are available in almost all large libraries.', 'Animals living on the ocean floor must be able to withstand water pressure that is far greater than the atmospheric pressure with which land animals live.']