Ideally, groups focused on environmental justice should be concerned

First point, a run - on occurs when you try to join a phrase with the main sentence with punctuation other than a comma such s period, semicolon or colon. A is a run - on but B is not, since it uses the comma.

Second, -And -is a co-ordinate conjunction its purpose is to join two equal things. In the exercise in front, the main issue is to find how new government projects will impact local populations; whether they specifically pose a burden is part of the main impact and not equal to the impact.

Third, when you use the co-ordinate conjunction, it is justified to skip the subject, provided , you can use the same subject of the main clause, which incidentally in this case is – groups- If you insert the subject - groups – in the second part you can see the absurdity of leaving the subject to imagination. The correct subject of the second part is the – projects – and unless this subject is mentioned, then the choice suffers unclear expression; that is why D is not correct

PS: May I request you not pre-empt the answer; we must get some good discussion before we know the answer.