In the following sentence, the blank is to be filled in with an appropriate word. Select the correct alternative out of the four options: "As a fitness ___________, Deepti is always preaching to her friends about the importance of working out."

Introduction / Context:
This vocabulary question checks your understanding of related word forms and how they fit into sentence structure. The sentence describes Deepti as someone who cares a lot about fitness and talks about it often. The blank follows the phrase "As a fitness _________," which gives a strong clue that the missing word should be a noun describing a person.

Given Data / Assumptions:

• Sentence: "As a fitness ___________, Deepti is always preaching to her friends about the importance of working out."
• Options: enthusiasm, enthusiast, enthusiastic, enthusiastically.
• The article "a" before the blank ("a fitness ...") signals that the blank should be a singular countable noun.
• We assume that Deepti is a person who strongly likes fitness.

Concept / Approach:
The correct choice must be a noun that refers to a person with a strong interest in fitness. "Enthusiast" is exactly such a noun; it means someone who is highly interested in or devoted to a particular activity or subject. "Enthusiasm" is a noun but names the feeling itself, not the person. "Enthusiastic" is an adjective, and "enthusiastically" is an adverb, neither of which can be used directly after "a fitness" in this structure.

Step-by-Step Solution:
Step 1: Notice the article "a" before the blank: "As a fitness _________". This requires a singular countable noun referring to a person or role. Step 2: Examine "enthusiasm": this is a noun, but it refers to the feeling of excitement, not the person who feels it, so "a fitness enthusiasm" is incorrect. Step 3: Examine "enthusiast": this is a noun meaning a person who is very interested in a particular subject, such as a music enthusiast or a sports enthusiast. Step 4: Insert "enthusiast" into the sentence: "As a fitness enthusiast, Deepti is always preaching to her friends about the importance of working out." This is natural and grammatically correct. Step 5: Examine "enthusiastic": this is an adjective and cannot directly follow "a fitness" in this way; we would say "an enthusiastic fitness trainer" instead. Step 6: Examine "enthusiastically": this is an adverb and is completely unsuitable after the article "a". Step 7: Conclude that "enthusiast" is the only option that fits both grammar and meaning.

Verification / Alternative check:
Consider similar patterns: "As a music enthusiast, he attends every concert," or "As a technology enthusiast, she reads gadget blogs daily." In each case, "enthusiast" refers to the person with a strong interest. Replacing "enthusiast" with "enthusiasm", "enthusiastic", or "enthusiastically" in those sentences would be ungrammatical. This confirms that "fitness enthusiast" is the correct and idiomatic phrase in the question sentence.

Why Other Options Are Wrong:
"Enthusiasm" is wrong because the sentence needs a person, not a feeling. "Enthusiastic" is wrong because it is an adjective and does not fit after "a fitness" without a following noun. "Enthusiastically" is wrong because it is an adverb, which cannot fill a noun slot.

Common Pitfalls:
Students sometimes focus only on the topic word "fitness" and quickly choose "enthusiasm" because they recognise it as being related to strong interest. However, ignoring the article "a" leads to grammatical errors. Always use the surrounding grammar clues (articles, prepositions, pronouns) to determine whether the missing word must be a noun, verb, adjective, or adverb.

Final Answer:
The correct word is enthusiast, giving "As a fitness enthusiast, Deepti is always preaching to her friends about the importance of working out."