why we cannot use 'most' before reason but we can use that before children in this example
Top notch questions:
cross out the one quantifier that cannot be used in each sentence.
1.There are (several/ most/ many) reasons why so many people have eating disorders.
2.a new study says that (most/ many / every ) children who watch tv for more than six hours a day may have problems with self-esteem as teenagers.
answers: 1.most 2.every

Question

why we cannot use 'most' before reason but we can use that before children in this example
Top notch questions:
cross out the one quantifier that cannot be used in each sentence.
1.There are (several/ most/ many) reasons why so many people have eating disorders.
2.a new study says that (most/ many / every ) children who watch tv for more than six hours a day may have problems with self-esteem as teenagers.
answers: 1.most    2.every

Answer

You use 'most' when you are talking about some large part of an even larger group.
In sentence 1, we cannot say 'most reasons', because there is not a large group of reasons we can measure against.  This would be correct.
Of all the reasons given for speeding, most of them involve lack of attention.
In this case we have the larger group of all reasons and the group included in that main on of reasons involving lack of attention.  This was not true in sentence 1.

In sentence 2, the total group is the group of all children who watch 6 hours or more of TV.  The smaller group is the number of children who lack self esteem - a smaller group than the total, but most of it still.

Answer

Your choices are correct: 1. MOST cannot be used; 2. EVERY cannot be used. Bravo!

Answer

for question number 1:
you could use either  "several", or "many."

question number 2:
I would use the words "most" or "many"