68. According to the text， the Sierra Club is most likely to be ______. (A) an environmental group (B) an information center (C) a travel service (D) a law firm

66. National parks like Yosemite in the U.S. find it increasingly difficult to meet the need of visitors because ________. (A) their transport management needs improving (B) they spend too much on their service systems (C) their service systems frequently go out of order (D) they need help from environmental organizations