Question

cross demand
substitute goods complementary goods
tea coffee
which of the following pairs of products are complements?
pens and pencils
butter and margarine
light bulbs and lamps
coffee and tea

Explanation:

Complementary goods are products that are used together, so an increase in demand for one leads to an increase in demand for the other. Substitute goods can replace each other.

• Pens and pencils: substitutes (can be used for writing interchangeably).
• Butter and margarine: substitutes (similar spreads).
• Coffee and tea: substitutes (beverage alternatives).
• Light bulbs and lamps: complements (light bulbs are used in lamps; you need a lamp to use a light bulb effectively, and a lamp needs a light bulb to function as a lighting device).

Answer:

light bulbs and lamps