单项选择题
A．is insignificant B．is enormous C．seems overestimated D．remains unknown
A．are yet to be proved B．are to be further studied C．are supported by scientific evidence D．are self-evident
A．their English is not good enough B．they are afraid they might meet with unfair judgment in these areas C．there is a wide difference between Asian and Western cultures D．they know little about American culture and society