We take your first two preferences (we want you to be able to study these where possible!) and look at this alongside the entry requirements for these subjects
to construct the offer (as outlined in the "Essentials and Admissions Process").
These preferences do not tie an applicant to studying these subjects within Natural Sciences!
The only exception is Chemistry. Failing to specify it as one of the first two preferences will result in the applicant being unable to study Chemistry while at Durham.