That sentence would be a great place to introduce my favourite letter in our beautiful language: ĥ!
Ĥo estas la plej sola litero, kiun vi iam ajn renkontos…
I wrote "arhxitekto" and it said I had a typo. Shouldn't it be accepted?
It should. Arĥitekto is an alternative form of arkitekto.
I thought all Esperanto nouns ended in "-o". Is "profesion" an exception?
No, it's not. The noun is indeed profesio, along with the accusative "-n".
Compare the following sentence, which uses esti rather than havi, and thus requires no accusative case:
Arĥitekturo estas bona profesio.
You are so right and actually it was an obvious answer. I totally confused with the english word "profession". Thanks.
Don't worry, we've all been there...