题目

________ the possible failure, I lowered the difficulty of the vocabulary choices.A.Concerned about B.Concerned withC.Concerning about D.Concerning with 答案：【答案】A【解析】。考查短语辨析和非谓语。句意：担心可能会失败，我降低了词汇选择的难度。A. Concerned about担心；B. Concerned with关心，与......有关；C. Concerning about 关于；D. Concerning with 关心。由句意可知，担心有失败的可能性，所以降低了选择难度，短语be concerned about“担心”符合语境，此处省去b下列哪种生物技术能有效地打破物种的界限，定向改造生物，培育新的农作物优良品种（ ）A．基因工程育种B．诱变育种　C．杂交育种D．单倍体育种