It will follow a general noun and is not set off by commas is true regarding a restrictive adjectival clause. Since this clause is restrictive, it means it is essential for the meaning of the noun and cannot be excluded.
the food supply in Elizabethan England
The entire paragraph is about the food supply in Elizabethan England. It describes how food was valuable because it was not always easy to acquire. Travel was more difficult in Elizabethan England than in present day so the food supply was limited to what was available close by. Food options also varied by season. Some due to when certain fruits and vegetables were ale to grow and others due to when the food could be carried to different markets.
Vietnam Veterans Memorial is a monument of 8000 square meters. It honors the members of the US Army who have died and are missing. Construction and manufacture was the cause of the controversy, which led to an additional construction. The memorial wall that was the cause of the controversy was designed by architect Maya Lin. The problem would be that the wall is black and without ornaments, then, it was lacking in resolving the national conflict over the war. It did not reflect the real circumstances that would speak about conflicting opinions about the war, as well as the minimalist design of the monument that diminishes the value of sacrifice of US soldiers. Some officials, among whom the most vocal were James Webb and H. Ross Perot, called it "the black wall of shame," "slapping in the face of those who served." At first they were supporters of Maya Lin's design, but later they became opponents seeing how the design looks. They also called it a "Nihilistic stone slab". Their claims were supported by the fact that Maya Lin is a young Asian student, and as such is not qualified to design such a monument.