ข้อสอบ TOEFL
ข้อที่ 6 / 21
Copper was one of the first metals to be mined on a wide scale, __________ it often occurs in nearly pure form and requires little refining.
then
as
as long as
คอร์สเรียนแนะนำ
฿2,990
฿3,740
หนังสือแนะนำ