Quick AADSAS LOR question - Weak Letter

I’m applying to 18 dental schools. All of them require 3 letters of rec, except for one that requires 4.

I have 3 strong letters I feel really confident about, and 1 that’s weaker. My question is:

Should I… A) Just submit the 3 strong letters to all schools, and drop the one school that requires 4? B) Submit all 4, knowing that some schools might read the weaker one?

Also, does AADSAS let you choose which letters go to which schools, or do all schools see all submitted letters?

Thanks in advance for any advice!