________thetimehewasthirteenye

发布时间：2020-07-28 00:50:59

________ the time he was thirteen years old, he advanced maths all by himself.A.At; learnedB.On; had learnedC.During; would learnD.By; had learned

网友回答

D
以上问题属网友观点，不代表本站立场，仅供参考！