I found my father a very hard man to understand when I was young. He was very short and thin and had large blue eyes. I could have loved him as I did my mother, but he seemed to hold us off so that we could not approach him or sit on his knee as love to do. I believe he had a hard life as a child, and I know that he left school at the age of ten and started to work. This made him an unsociable man, unfriendly even to the people closest to him. I never knew him to have a close friend as the other men did. Everything he did had to be precise. If he chopped the sticks for the fire, each stick would be the same length and thickness as all the others, and they would all be stacked (堆放) without one out of place. His motto (座右铭) was "If a thing is worth doing, it is worth doing well". In our household his word was law and nobody dared dispute it. My father would take off his clothes and get into bed on Saturday afternoons, leaving my mother to mend his working clothes. This she disliked very much, for the clothes were dirty from the work he had been doing and she hated handling anything that was not clean. The writer thought ______ made her father unsociable.

A. an unhappy childhood
B. a lack of friends
C. no interest in hobbies
D. not smoking or drinking