Nice combo brother. But I think that environmental science is very technical subject though aspirants don't pay heed to this thing. That's just one and only reason for low scores in this subject. Because aspirants prepare it like any other general subject and attempt paper good too(according to them it's a good attempt but for examiner it's whole different scenario). But at the end ,what examiner needs is technical answer ,not general one.
I think educational background is required for this subject.

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''Sufficient for us is Allah , and He is the best Disposer of affairs" Al-Quran