In standard English usage, the word "solely" most nearly means which of the following?

Introduction / Context:
Vocabulary questions often focus on common adverbs and adjectives that appear in everyday reading but can still confuse learners. The word "solely" is frequently used in news articles, formal writing, and instructions. It has a precise meaning related to exclusivity. This question asks the learner to identify which option best captures that meaning. Understanding the adverb "solely" helps in interpreting sentences about responsibility, causes, and conditions, such as "He is solely responsible for the project" or "The decision was based solely on merit".

Given Data / Assumptions:
- The target word is "solely", an adverb.
- The options include ideas of excluding, including, being the only one, rivalry, and rarity.
- The question asks for the meaning that is closest to common English usage.
- We assume that the context is neutral, not idiomatic or slang usage.

Concept / Approach:
"Solely" comes from the adjective "sole", which means single, only, or alone. The adverb "solely" therefore means "only" or "exclusively". When something is done solely for one reason, it means there is no other reason involved. When responsibility lies solely with one person, no one else shares that responsibility. The approach to solving this question is to recall this idea of being the only one or being exclusive, and then to eliminate options that talk about inclusion of everyone, competition, or rare events, which are unrelated concepts.

Step-by-Step Solution:
Step 1: Recall examples such as "She did the work solely for charity". In this sentence, the meaning is "only for charity and for no other reason". Step 2: Check option A, "Exclude completely from a group". This describes an action and is closer to the verb "exclude", not the meaning of "solely". Step 3: Look at option B, "Include everyone without exception". This is almost the opposite of exclusivity and does not match the idea behind "solely". Step 4: Consider option C, "Only, and nothing or no one else". This directly expresses the sense of exclusiveness that "solely" carries. Step 5: Option D, "Rival or compete with someone", is related to competition and is not connected to the meaning of "solely". Step 6: Option E, "Occur very rarely", describes frequency, whereas "solely" does not mainly express how often something happens. Step 7: Therefore, option C is the correct match for the meaning of "solely".

Verification / Alternative check:
To verify, replace "solely" with "only" in some common sentences. For example, "He is solely responsible for the mistake" becomes "He is only responsible for the mistake", and "The scheme is solely for students" becomes "The scheme is only for students". In each case, the meaning stays the same. This quick substitution test is a reliable way to check the meaning of many words in context. None of the other options can replace "solely" in such sentences without changing the meaning, which further supports option C as the correct choice.

Why Other Options Are Wrong:
Exclude completely from a group: This is a verb idea and does not represent the adverb "solely", which modifies how something is done rather than who is removed.
Include everyone without exception: This is closer to words like "universally" or phrases like "for all", and conflicts with the exclusive sense of "solely".
Rival or compete with someone: This describes a relationship between people or organisations, not the idea of doing something alone or exclusively.
Occur very rarely: This is about frequency, which is the domain of adverbs like "rarely" or "seldom", not "solely".

Common Pitfalls:
Learners sometimes confuse "solely" with "sincerely" or other adverbs that appear in formal letters and official language. Another pitfall is to assume that any serious sounding adverb must involve difficulty or rarity, which leads to picking an option about rare events. To avoid mistakes, it helps to connect "solely" with "sole owner" or "sole survivor", both of which clearly mean "only owner" and "only survivor". This mental link reinforces the idea of one person or one reason and leads to the correct answer more reliably.

Final Answer:
In standard English usage, "solely" most nearly means only, and nothing or no one else.