Which of the following statements about the movement of earth's atmosphere is correct? select one:

a. a column of warm, less dense air produces high pressure at the earth's surface.
b. cold air is less dense than cool air so it tends to sink toward the earth's surface.
c. the movement of air within the atmospheric convection cells generates the wind belts.
d. warm air is denser than cool air so it tends to sink toward the earth's surface.
e. a column of cool, dense air produces low pressure at the earth's surface.

The chart shows the costs and shipping times for materials that a company needs to build a new product. which describes the best trade-off if the company needs to start building their product within the next two years? they should order the domestic materials because it is always best to choose the fastest shipping time. they should order the imported materials because it is always best to choose the lowest cost for materials. since the shipping time is longer, they should order the domestic materials because the additional cost is worth it to get the materials in time. even though the shipping time is longer, they should order the imported materials because they are less expensive and should arrive in plenty of time to build the product.