Why was Einstein's mother worried when she saw him in childhood?

Correct answer: Because his head seemed unusually large

In the chapter, Einstein’s mother was worried because his head appeared unusually large when he was a baby. This detail helps introduce him as a child who seemed physically and behaviourally different from ordinary expectations. Therefore option C is correct. The question is not asking whether he was intelligent later or why he became famous; it asks about his mother’s immediate childhood concern. Option A describes running and option B describes singing, neither of which is given as the reason for her worry. Option D is also unsupported: the text does not say that he never slept. The correct response must stay close to the specific childhood observation mentioned in the biography.