I would say that geography meant that Greece was very rocky so agriculture was difficult so Greece would have to rely on trade for some of its food. On the other hand, Greece has many islands in the Mediterranean which probably allowed the residents to catch fish and supplement their diet with that and perhaps trade fish for agricultural products.
"Nasser's decision threatened British and French stock holdings in the Company and, as the Canal afforded Western countries access to Middle Eastern oil, also threatened to cut off Europe's oil supply." according to an article.
