单选题 The most crucial problem any economic system faces is how to use its scarce resources.
  • A. puzzling
  • B. difficult
  • C. terrifying
  • D. urgent


【正确答案】 D
【答案解析】[解析] crucial：至关紧要的，和urgent(紧急的)含义最接近；puzzling：(使)迷惑的、(使)为难的；difficult：困难的；terrifying：使感到恐怖的。