单选题 The research scientists often meet with problems ______ new types of instrument for their solution.
A. requiring B. required C. to require D. being required

【正确答案】 A

【答案解析】[解析] 此题应选现在分词requiring，在句中作定语，修饰problems，相当于定语从句...problems which require...，因为它们在逻辑上是主动关系，所以应选现在分词。句意为：“科研人员常常遇到需要新型仪器才能解决的问题。”