Given the Following Sorites: No S Are A

Multiple Choice

Given the following sorites: No S are A.
All N are A.
All T are N.
Some R are T.
Some R are not S.
This sorites is:

A) Invalid because only one premise is negative.
B) Invalid because one of the middle terms is undistributed.
C) Invalid because a term is distributed in the conclusion but not in the premise.
D) Valid because no rules are broken.
E) Valid because a negative premise requires a negative conclusion.