In the following sentence, one part may contain a grammatical error. Read the sentence and the labelled parts carefully and identify which segment is incorrect, if any. The sentence is: I was first (A) / to reach the school (B) / today. (C) / No error. (D)

Introduction / Context:
This grammar question examines the correct use of articles with ordinal numbers in English. The sentence describes someone being the earliest person to arrive at school on a particular day. The key issue is whether the phrase uses the correct article with the ordinal adjective first. Many learners omit necessary articles in front of ordinal numbers, which leads to unnatural or incorrect English, especially in formal writing and competitive examinations.

Given Data / Assumptions:

• Original sentence: I was first (A) / to reach the school (B) / today. (C) / No error. (D)
• The sentence is divided into four labelled parts A, B, C, and D.
• Part D indicates the option that no segment contains an error.
• The task is to identify the segment that has incorrect or incomplete grammar.

Concept / Approach:
In English, ordinal numbers like first, second, and third often need the definite article the before them when they refer to a specific position in an ordered group. When the speaker means that among all students arriving at school that day, this person occupied the earliest position, the usual expression is I was the first to reach the school today. Without the, the phrase I was first to reach the school sounds incomplete and less natural in standard English. Therefore, the error lies in the omission of the definite article in Part A.

Step-by-Step Solution:
Step 1: Read the full sentence in one flow: I was first to reach the school today. Step 2: Focus on Part A, I was first. This contains the ordinal first but does not include an article. Step 3: Recall the correct expression I was the first to do something when we talk about a specific act among a group. Step 4: Check Part B, to reach the school, which functions correctly as an infinitive of purpose and is grammatically sound. Step 5: Check Part C, today, which is an adverb of time and correctly placed at the end of the sentence. Step 6: Decide that only Part A has the error and that it should read I was the first.

Verification / Alternative check:
To verify, we can compare similar sentences. For example, I was the first to finish the exam, she was the second to arrive, and he was the last to leave. All of these use the before the ordinal number. If we remove the article, the sentences sound grammatically weaker and less natural. Similarly, sentence patterns in textbooks and exam material consistently include the in such cases. Therefore, adding the before first in Part A is the correct correction, and this confirms that Part A is the only erroneous segment.

Why Other Options Are Wrong:
to reach the school: This phrase correctly explains the action and does not contain any error in structure or preposition use.
today: This adverb of time is properly used at the end of the sentence and is grammatically acceptable.
No error: Selecting this would incorrectly state that the sentence has no mistake, even though Part A omits a necessary definite article.

Common Pitfalls:
Learners sometimes omit articles in English because many other languages do not use them in the same way, or because they assume that short sentences without articles are acceptable. Another pitfall is not recognising the special behaviour of ordinal numbers, which often require the definite article the when they specify a particular place in an order. To avoid these mistakes, it is useful to remember set patterns such as the first to arrive, the second highest, and the last one in line, and to apply these patterns in new sentences.

Final Answer:
The incorrect segment is I was first, which should be corrected to I was the first.