Although the earliest surviving Greek inscriptions written in an alphabet date from the eighth century B.C., the fact that the text of these Greek inscriptions sometimes runs from right to left and sometimes from left to right indicates that the Greeks adopted alphabetic writing at least two centuries before these inscriptions were produced. After all, the Greeks learned alphabetic writing from the Phoenicians, and presumably, along with the alphabet, they also adopted the then-current Phoenician practice with respect to the direction of text. And although Phoenician writing was originally inconsistent in direction, by the eighth century B.C. Phoenician was consistently written from right to left and had been for about two centuries.
In the argument given, the two portions in boldface play which of the following roles?
先找这个题的最终argument: ...that the Greek adopted alphabetic writing at least two centuries before these inscriptions were produced.
第一个加粗的地方是在indicates这个argument,所以第一个肯定是evidence/support之类的东西。
之后说的是希腊人从Phoenician那儿学的文字和书写方式,而Phoenician在8th century已经从右到左写了两个世纪, 这个又支撑了:所以希腊人不是在8th century才学的。