题目

关节既牢固又灵活，与此功能无关的是（ ） A . 关节面上覆盖着一层关节软骨 B . 关节周围的肌肉能收缩和舒张 C . 关节周围由关节囊包裹着 D . 密闭的关节腔内含有滑液 答案：B Large quantities of information, as well as some timely help ________ since the organization was built.     A. has offered                    B. had been offered     C. have been offered                      D. is offered