Question

He started _____to ride a bicycle when he was 3 years old.Ato learn Blearn CcleaningDlearns

Answer 1

答案：He started 【learning】to ride a bicycle when he was 3 years old.

解析；start doing sth.开始做某事.【已经开始做了.】

start to do sth.开始去做某事.【还没有开始做.】

从when he was 3 years old.可以知道已经开始做了.

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Answer 2

选C，learning
start doing sth 开始做某事
He started _learning_ to ride a bicycle when he was 3 years old
他三岁时开始学骑自行车。