题目

如图，AB∥CD，AB∥EF，EG平分∠BED， ∠B=45°， ∠D=30°．求 ∠GEF的大小． 答案：解：因为AB∥CD，AB∥EF，所以EF∥CD，所以内错角 ∠FED= ∠D=30°．又因为AB∥EF，所以内错角∠FEB=∠B=45°，从而， ∠BED=∠FED+∠FEB=75°．因为EG平分∠BED，所以∠BEG= 12 ∠BED=37.5°．从而 ∠GEF=∠BEF-∠BEG=45°-37.5°=7.5°．所以 ∠GEF为7.5°． At last he _____ finish the work ahead of time.        A. could                                                   B. was able to                                           C. could be able to                             D. can be able to