"He does not want to cook it because it is not tasty."
Translation:הוא לא רוצה לבשל את זה כי זה לא טעים.
What does איננו mean (used instead of לא in one of the correct options in the multiple choice exercise)?
The inflections of "אין" can be used for negation instead of "לא" in present tense, and they're more formal. איננו is an inflection of the word "אין" for third person singular masculine (הוא). There's a table of inflections in the Formal lesson. If you haven't reached it yet there's also one here https://en.wiktionary.org/wiki/%D7%90%D7%99%D7%9F