"Ini adalah penelitian tentang polusi udara di Jakarta."

Translation: This is a research about air pollution in Jakarta.

[Leapy3]

It would sound much better in English as "This is research about air pollution in Jakarta" or "This research is about air pollution in Jakarta"

[S9N1t]

Yes, in fact you can't say "a" research in English. It's like sugar or salt, uncountable. It should be "This is research about ..."

[Harvey384140]

This research is about the pollution in Jakarta should be accepted Duolingo's answer is very awkward and would not be used by native speakers.

[LlewGreen]

'This is A research about...' Really?