"The women went in a group to the bathroom."
Translation:La virinoj iris ope al la necesejo.
No. -op- is generally combined with numbers. Sesope - by sixes. Kvarope - in groups of four.
Note, last I checked, the system accepted both "goes in groups" and "goes as a group" for this sentence, even though these English phrases mean different things. I've brought this to the attention of the course administrators. I don't know if they intend to fix it in the next version (or whether they've already fixed it.)