The socket stays on that wall. Should be correct too. Given that Duolingo uses often bizarre and low frequency sentences, this definition should be accepted.
"Honey, when the electrician comes, let's have him move the socket."
"No dear. The socket stays on that wall."
Technically an outlet is "in" a wall, as well as "on" a wall. Should I really be marked off for saying it's in the wall?
"In THE wall" isn't the correct translation of this sentence, it should be "in THAT wall".
Sockets are not considered permanent enough fixtures in Portuguese so likely "stays" (located), or esta the less permanent form of "to be" in Portuguese is accepted.
I don't see why "There is a socket in that wall" would be marked wrong. I know about "ha" but this is a good English translation of the Portuguese
There is a socket in that wall is more general than, The socket is in that wall.
But by now you probably have figured that all out, so this is for all those who are new readers. :)
In addition to 'outlet' it could be called socket, or powerpoint (Australia)
Generally in American English we say that the outlet is "on" the wall rather than "in".
Ficar also means to stay so why not - the socket stays on that wall? Baffeled and bomboozeled by this section