是定语从句.先行词为1966,把先行词还原到后面的句子中为:People created a new festival so that African Americans would be able to celebrate their history and culture in 1966.
when后面的整个句子是对先行词的修饰限制.
是定语从句.先行词为1966,把先行词还原到后面的句子中为:People created a new festival so that African Americans would be able to celebrate their history and culture in 1966.
when后面的整个句子是对先行词的修饰限制.