The Keeling Curve in Figure 25

question 108

Multiple Choice

The Keeling curve in Figure 25.1, below, shows that while CO₂ levels oscillate on an annual basis, overall CO₂ levels increase from year to year. Why has this trend continued in the last 50 years?

• A)increasing rates of aerobic respiration associated with the rise in world population
• B)decreasing rates of oxygenic photosynthesis by plants and algae
• C)clearing of forests to create agricultural land outside the tropics
• D)combustion of fossil fuels

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Definitions:

International Trade

The exchange of goods and services between countries, involving exports and imports.

Quota

A government-imposed trade restriction that limits the number or monetary value of goods that can be imported or exported during a specified period.

Sugar

A sweet-tasting, soluble carbohydrate used commonly as a sweetener in food and drinks.

Tariff

Tax on an imported good.