Which one of the following can be inferred from the passage about pumps that are currently available to boost the natural pressure of crude? A. The efficiency of these pumps depends on there being no gas in the flow of crude. B. These pumps are more efficient when the crude is less subject to sudden increases in the proportion of gas to liquid. C. A sudden change from solid to liquid in the flow of crude increases the efficiency of these pumps. D. The proportion of liquid to gas in the flow of crude does not affect the efficiency of these pumps. E. A sudden change from liquid to gas in the flow of crude increases the risk of explosion due to rising pressure inside these pumps.