Question 9: Find mistakes and correct Mining over 2,000 years ago, copper is one of earliest known (metals.
Explanation: The structure is shortened to: S + V1 + O, S + V2 + O (two subjects are one; V1, V2 have the same tense)
+ When V1 is in the active form, we shorten it to: V-ing + O, S + V2 + O
+ When V1 is in passive form, we reduce it to: P(II) + O, S + V2 + O
Edit: Mining => Mined
Mined more than 2000 years ago, copper is one of the earliest known metals.