SAT改错题
the name"transferware" (comes form a nineteenth-century technique for which) a pattern is engraved onto a copper roll,printed on tissue paper,and transferred onto earthenware dishes.
（）内为要修改的
答案是comes from a nineteenth-centry technique whereby,请问whereby在此处什么意思?如果改成非定语从句的正常句子应该是什么?