Which are corrrect for choosing proppant A: for low permeability formations,the fracture mainly is requires to increases the length B: for low permeability formations,the fracture mainly is requires to increases fracture conductivity C: for medium or high permeability formations,the fracture mainly is requires to increases the length. D: for medium or high permeability formations,the fracture mainly is requires to increases fracture conductivity.

ENUM类型的字段level定义为（LOW、MIDDLE、HIGH），ORDER BY level asc的顺序是 A: HIGH、LOW、MIDDLE B: LOW、MIDDLE、HIGH C: MIDDLE、LOW、HIGH D: HIGH、MIDDLE、LOW

以下各句正确的是__________。 A: An increase in demand is likely to cause a rise in prices. B: Increases in demand usually lead price increases. C: If demand increases; as a result, prices tend to rise. D: Increases in price are often resulted by increases in demand.

what is Market-Skimming pricing? A: Set a low initial price in order to penetrate the market quickly and deeply. B: • Set a high price for a new product to skim revenues layer by layer from the market. C: determine the price according to the perceived value of the buyer to the product.

The act of buying at a low price in one place and selling at a high price in another place is called relative pricing.