单选题 Every means ______ tried but without much result.
  • [A] is
  • [B] are
  • [C] has been
  • [D] have been


【正确答案】 C
【答案解析】考查时态和主谓一致。means用作单数，故谓语动词应用单数形式；而由but后的分句句意可知方法已经试过了，应用完成时态。结合起来可知选[C]。