| _____ he was fifteen year old, he _____ advanced maths all by himself. A. Each time; had learned B. By the time; learned C. Each time; learned D. By the time; had learned |
| _____ he was fifteen year old, he _____ advanced maths all by himself. A. Each time; had learned B. By the time; learned C. Each time; learned D. By the time; had learned |
| D |