Please help me to understand the first blank as well as full sentence

Please help me to understand the first blank as well as full sentence

I dont for sure know what the answer is, but this is what i think.
Here’s my thought process:
To begin with, I’d put the division word at “that” after the word “claims”.

  1. Blank 1:
    It says “sad but just indictment”, meaning the textbooks have done something wrong and are indicted for it, but it’s justified. “That they report as _____ claims” suggests that the textbooks were indicted for some claims, and textbooks usually prefer putting irrefutable claims OR facts, to educate children.
    Eg: Sun rises in the east

  2. Blank 2 & 3: We’re carrying the idea of the claims being debated
    It’s a support because of the word “that”, after claims. In addition within the second sentence, “or” also suggests a continuation of the same support logic.

Claims that historians hotly debate” suggests something of controversy (not to be confused with the first blank). Thus, the blanks would be contradicted & reliable. These two words put together suggest the same as claims being “hotly debated”.

Hope this helps.

What refers to they in the sentence? I picked controversial for 1st blank but answer is factual

My bad.

So “they” refers to the textbooks themselves. And as I mentioned in the explanation, the reason “factual” is correct is because the textbooks portray information as facts. Like think about it, would a textbook try educating a child with information that maybe correct or is definitely correct? Definitely right.

Thats why “they frequently report as factual claims

So simply the sentence means history text book contains facts which are debatable like they are twisting history?

So while the claims themselves might be controversial because they don’t conform to reliable sources, they (claims) are interpreted as facts by the textbooks.