1)The flags placed in the room will be ( ) the school sports

1)The flags placed in the room will be ( ) the school sports meet .
A)used for B)used as
请说一下理由
2)Let's look ( ) this matter together .
A)into B)through
请说一下理由
3)Physics is ( ) ,if not more difficult than ,Chinese .
A)as difficult as B)so difficult as
请说一下理由