单项选择题Black people were first brought to America from Africa as ______.
单项选择题In English all the prefixes are ______ morphemes.
单项选择题After the American Revolution, ______ became the first capital of the United States, being already the largest city in North America.
单项选择题The novel ______ by Samuel Richardson is considered the first English psycho-analytical novel.
单项选择题In general, children's holophrastic sentences begin ______.