I am on holiday in Sicily and clearly my attention was elsewhere when I posted. Thanks for spotting the error which I will try to correct when I get back. If/when you spot other errors please point them out. It is curious how my concentrating on whether the word order could be at fault blinded me to the obvious mistake in vocabulary. 
Happy holidays! Sicily sounds wonderful! Again, thank you so much for publishing this key, it helps me a lot to spot many of my own mistakes.
But here I have another doubt. It is about a sentence 2 form ex. E
If creo is a verb which has double accusative in active voice and double nominative in passive, shouldn’t “Marius, who was often elected consul, was a great general” be rather “Marius, qui consul saepe creabatur, dux magnus fuit” instead of “qui consulem saepe creabat”?
While Seneca is basking in Taormina, let me answer for him. His key is right: your translation would mean “who often elected the consul”. As you said, it should be double nominative in the passive.
Thanks Bedwere! Although I have visited Taormina I am based in Catania - a much underrated destination. Taormina has clearly seen better days and I don’t think I will be returning there.
Hi, bedwere. Thanks for your reply!
I’m sorry, but still, I think my translation “qui consul creabatur” means “who was elected consul” and there is a mistake in the key, because creo is not a deponent verb (so with passive form “creabatur” we should have two nominatives, “qui” and “consul”). Compare it with the correct active phrase 11, ex. F: The citizens themselves wished to make him consul. Cives ipsi eum consulem creare volebant. Here you have two accusatives and the active infinitive “creare”.
I long since corrected seneca’s original slip (April 5 2023, I just checked), but it must have escaped both his and bedwere’s subsequent attention. There was some distracting fuss about quantity marks at the time I remember, and about tense.
Incidentally, I second seneca’s commendation of Catania. Avoid Taormina!
Sorry, I misread. I thought the key had “qui consul creabatur” (which is right), not your translation. We’ll wait for Seneca to correct the key.
No problem! 
I’m very grateful to you all for your help and glad if I can also be useful.
Here I have a little curiosity remark about exercise H, 42 “in the power of the enemy - In potestate hostium”. I find no error in the key. I’ve just found another possible way of translating the frase using a preposition “penes” which means exactly “in the power of”. Ex.: « Cum penes unum est omnium summa rerum, regem illum unum vocamus, et regnum ejus rei publicae statum ». Cic. Rep. 1, 42
P.S. It seems that also alternative translation is possible in K, 14 “They escaped from prison without my knowledge - Inscio me ex carcere elapsi sunt”. Again, I see nothing wrong with the key. The alternative possibility I came across is to translate “without my knowledge” using preposition “clam” - clam me. https://logeion.uchicago.edu/clam
Hi again Iulia,
Yes certainly many of these exercises have alternative possible answers. Some were discussed at the time. Latin did not stay still, and I wanted us to avoid too much Plautine usage in favor of classical, in line with the intention of the exercise. Words like penes and clam are not exclusively Plautine, to be sure.