题目

Last summer I took a course on________. A. how to make dresses        B. how dresses be made C. how to be made dresses D. how dresses to be made   答案：A不定式短语的构成由疑问代词what，which或疑问副词when，where，why，how等接不定式构成，疑问代词傲不定式的宾语，疑问副词做不定式的状语。如：I don’t know what to do / how to do ito 不定式短语的作用相当于名词性的从句，在句中可做主语，宾语和表语。如图所示，∠AOP=∠BOP=15°，PC∥OA，PD⊥OA，若PC=4，求PD的长．