Which of the following is a limitation to fully efficient markets（）

A. The gains to be earned by information trading can be less than the transaction costs the trading would entail.

B. In general, for securities with smaller transaction costs, the deviations from informationally efficient prices are greater than for securities with larger transaction costs.

C. There are no limitations to fully efficient markets because the trading actions of fundamental and technical analysts are continuously keeping prices at their intrinsic value.

离心泵按叶轮吸入方式分（）、双吸泵。