The mixing of surface water and deep water in the oceans that occurs because of differences in salinity is known as (a) upwelling. (b) a gyre. (c) the El Nino-Southern Oscillation. (d) an isocline. (e) thermohaline circulation.

A produce grower is purchasing fertilizer containing three nutrients: A, B, and C. The minimum weekly requirements are 80 units of A, 120 of B, and 240 of C. There are two popular blends of fertilizer on the market. Blend I, costing $8 a bag, contains 2 units of A, 6 of B, and 4 of C. Blend II, costing$10 a bag, contains 2 units of A, 2 of B, and 12 of C. How many bags of each blend should the grower buy each week to minimize the cost of meeting the nutrient requirements?

The vertical movement of cold, nutrient-rich water from the ocean depths to its surface is called a. upwelling. b. downwelling. c. tides d. surface currents.