His ______ with computers began six months ago.(2007年中国科学院考博试题)

单项选择题Although most universities in the United States are on a semester system which offers classes in the fall and spring, some schools______ a quarter system comprised of fall, winter, and summer quarters.(2004年西南财经大学考博试题)

单项选择题The custom is ______ in the belief that a new pregnancy — through its detrimental effect on breastfeeding — would endanger the mother’s health.(2002年10月中国科学院考博试题)