Between the two generations, it is often not their age, _________ their education that causes misunderstanding
A.likeB.asC.orD.but在线课程D
not...but...意为“不是……而是……”。it is...that...构成强调句,对“their age,but their education”进行强调,表示“不是他们的年龄而是他们的教育引起误解”。like 意为“像……那样,和……一样”；as 意为“作为,当……的时候”；or 意为“或,或者,还是,抑或是”。