Final answer:
A short supply of petroleum occurs when the demand is high, leading countries to rely on other nations that may have an overabundance of that resource.
Step-by-step explanation:
A short supply of petroleum occurs when the demand is high, leading countries to rely on other nations that may have an overabundance of that resource. This is because petroleum is a finite resource and its reserves are being depleted. The United States, for example, is presently unable to support its petroleum needs from domestic resources alone, leading to a reliance on imports.