"He was born in 1985"
Translation:Alizaliwa mwaka elfu moja mia tisa themanini na tano
numbers are adjectives, some take prefixes and some don't. "elfu moja" = one thousand, "mia tisa" = nine hundred, "themanini na tano" = eighty five. the "na" only goes between the tens and ones digits, unless the last two digits are divisible by ten, in which case it goes between the hundreds and tens digits, and so on.
In the previous question, "tulizaliwa mwaka elfu moja mia tisa na themanini" was the correct answer and leaving out "na" was marked wrong. Could it be that "na" is required before the last number: 10s or 1s.
The lesson material says specifically that it's optional, "mwaka elfu moja mia saba (na)* ishirini", but, apparently not.