Why is the answer "Az" rossz ... ?
The pronoun az doesn't lose its 'z' before a consonant the way the definite article az does.
Oh! I was thinking that in this situation "az" was being used as "the" but here it means "that". I get it. Thank you!
Can't I use "amelyik" here? It seems like every one of the conjunctive sentences in the later lessons uses "amelyik" when the subject of the main clause uses "az a", except for in this sentence.
Yes, you can.
Why is it "ami" and not "amelyik"?
What is the difference between 'ami' and 'aki'?
Aki is for people (or anything that you would use "who" with - it is derived from ki, meaning who)
Ami is for inanimate things (or anything that you would use "what" with - it comes from mi)