(c) Error: can | Correction: could
The sentence refers to past ability, so the past modal "could" is correct instead of "can."
When a sentence expresses ability in the past (signalled by "when I was young"), the modal verb must also be in the past form. "Can" is present tense; "could" is its past equivalent. This is a tense-consistency error — a common grammar question type in CBSE board exams.