Parallelism, Use of auxiliary verb
Solution 1:
At current prices, oil in the Antarctic may be worth drilling for, if [wells can be dug there] and [environmental concerns ___ addressed].
The sentence contains what is known as 'gapped coordination', where the middle part of the second coordinate is missing but recoverable from the corresponding part of first coordinate.
The gap, marked '____' , is understood by reference to the first coordinate; in this case "can be".
The fact that gapping is appropriate here demonstrates that the coordinates have parallel structures.