The idea for the new machine came to Mr．Baker ________ to his invention recently．
A.while devotingB.while devotedC.while he was devotedD.while devoting himself．在线课程C
解析：
while后主语及助动词不能省略，因为两句主语不一致。如主语一致，则：Mr Baker thought of the idea for the new machine (B / D) to his invention recently.