Mary could play piano when she was ten years old 这句话哪里错了?

Mary could play piano when she was ten years old 这句话哪里错了?
Mary could play piano when she was ten years old 这句话哪里错了?

Mary could play piano when she was ten years old 这句话哪里错了?
play the

玛丽10岁的时候就会弹钢琴了。

少了the，乐器前面要加the

是play the piano，表示弹西洋乐器前要加the

应该是play the piano
ten years' old
不知前半部分加上already会不会更贴近文意？

缺少the ，乐器前必须要加上the
而球类则不能加the
play the violin
play soccer