How Are the Obligations of Sellers/lessors and Buyers/lessees Are Determined

How are the obligations of sellers/lessors and buyers/lessees are determined?

A) The obligations of the parties are determined by the terms the parties outline in agreements, but not by custom or rules outlined by the UCC.
B) The obligations of the parties are determined by the rules outlined by the UCC, but not by terms the parties outline in agreements or by custom.
C) The obligations of the parties are determined by terms the parties outline in agreements and rules outlined by the Uniform Commercial Code, but not by custom.
D) The obligations of the parties are determined by the rules outlined by the UCC and by custom, but not by terms the parties outline in agreements.
E) The obligations of the parties are determined by the terms the parties outline in agreements, custom, and rules outlined by the UCC.