In the following question, out of the four alternatives, choose the one which can be substituted for the given words/sentence. A mixture of dried, naturally fragrant plant material, used to provide a gentle natural scent inside buildings, especially in homes and other residential spaces.

Introduction / Context:
This question deals with vocabulary related to pleasant smells and home decoration. The description given is "a mixture of dried, naturally fragrant plant material, used to provide a gentle natural scent inside buildings." This is a fairly specific definition that points to a particular decorative and aromatic product commonly used in bowls or decorative containers.

Given Data / Assumptions:

• The substance is a mixture, not a single liquid or gas.
• It uses dried plant material such as petals, herbs, and spices.
• The purpose is to provide a natural scent indoors.
• The options are potpourri, perfume, scent, aroma, and incense.
• Only one term precisely refers to a mixture of dried plant materials used decoratively.

Concept / Approach:
The word "potpourri" refers to a mixture of dried petals, herbs, spices, and other plant parts that emit fragrance over time. It is usually displayed in an open bowl or fabric sachet in homes to make rooms smell pleasant. While perfume, scent, aroma, and incense are all associated with pleasant smells, they do not match the exact form and description of a dried mixture placed around buildings.

Step-by-Step Solution:
Step 1: Focus on the word "mixture" and on the detail that it consists of dried plant material.Step 2: Note that perfume is generally a liquid fragrance, usually alcohol based and applied on the body.Step 3: Recognise that "scent" and "aroma" are general words for smell, not names of a specific product made of dried materials.Step 4: Remember that potpourri is exactly a decorative mixture of dried, fragrant plants placed in bowls or containers to freshen indoor air.Step 5: Therefore, potpourri is the correct one word substitute for the given description.

Verification / Alternative check:
Imagine entering a living room where there is a shallow bowl on the table filled with dried rose petals, lavender, orange peel, and spices, giving off a gentle fragrance. That bowl contains potpourri. You would not normally call that bowl "perfume" or "aroma." Instead, you would say "This potpourri smells wonderful." This visual test confirms that potpourri is the only option that matches the definition fully.

Why Other Options Are Wrong:
Perfume is a manufactured liquid fragrance, not a dried mixture. Scent and aroma describe smells in general and are often used as uncountable nouns rather than the name of a specific mixture. Incense consists of sticks, cones, or powdered material that is burned to produce smoke and fragrance, which is different from the passive fragrance of potpourri. None of these other options matches the idea of dried plant material in a bowl used to scent rooms naturally.

Common Pitfalls:
Students sometimes quickly choose "perfume" or "incense" because these words are strongly associated with fragrances. However, the question requires close attention to the physical form and usage of the material. Whenever a definition mentions dried petals or herbs in a decorative bowl, potpourri is the correct and precise term to remember for exams.

Final Answer:
potpourri