"It is an object."
Translation:C'est un objet.
Because we registered "un truc" as a valid alternative for this sentence. The computer checker scans your answers from left to right, sign by sign, and stops when there is a mistake. Then, it looks for the closer alternative translation.
In this case, it did not do a good job, because since your mistake was on the article, it would have been more logical to tell you that "objet" is masculine and just suggest "un objet" instead of "un truc".
"C'est un objet" was also marked wrong ... it wanted "chose" instead of objet for object ... why?
"C'est un objet" is the preferred translation that you can read at the top of this page. "C'est une chose" and "c'est un truc" are also accepted translations. If you got a multiple-choice exercise, maybe 2 correct options had to be ticked.
The system screens your answers sign by sign. The first wrong sign sets off a search for the nearest correct answer from the list of accepted translations we fed the system with.
So, if you propose "C'est une objet", the first wrong sign is the O of objet, because "une" is correct, as long as it is followed by the feminine noun "chose".
Instead of telling you that "un objet" is masculine and correcting the article, the system was programmed to keep as many correct signs as possible and offer the closest correct answer possible after your last correct sign.