I had to hit all three of the available faults as the one I wanted The English is unnatural wasn't there.
It is more usual to say The gladiators are accustomed to fighting, using the gerund rather than the infinitive, since the to in this case is a preposition (I think that the correct term) attached to Accustomed, rather than the "to" associated with the English infinitive.
I tried Gladiators are accustomed to fight lions and Gladiators are accustomed to fighting lions
The first is passive: someone is habituating the gladiators so that they will fight lions
The second is an active statement of fact: the gladiators are already used to fighting lions.
It's subtle, but could we have "fighting" as an alternative answer, if it's not already (I used tiles). Thank you.
I had suggested that all report boxes include a free write area, but a course contributor told me that people unlash all sorts of abuse. I think they should make you sign your username to contain the abuse. It's strange that often we are given the most probable four reasons for reporting, but just when you need the last one of them, the English sentence in this case, it's not there!
This has come up in the German course. Reports are anonymous to course creators. In the case of "my answer should have been accepted" the system automatically emails everyone who reported a given answer. One of the Latin course creators has said that they don't know and can't tell whether it's a group of people, or just one dedicated person, reporting... I forget what, I think it's every single use of the copula being required in the Latin.