Concept: This question tests basic English grammar, including subject-verb agreement, use of articles, countable/uncountable nouns, and common expressions.
Step 1: Analyze each sentence for grammatical correctness
(1) He has a shirt and two pants.
The word "pants" (referring to trousers) is a plural noun that typically refers to a single garment. While we say "a pair of pants," saying "two pants" to mean two separate garments is common in some contexts but can be ambiguous. More precisely, one might say "two pairs of pants." However, the main issue here is that in standard English, "pants" is often treated as a plural form requiring a plural determiner if counting items, or used with "pair of." For a single item, it's "a pair of pants." So, "two pants" might be considered informal or slightly awkward compared to "two pairs of pants." Let's check other options.
(2) I came, I saw, I conquered.
This is a famous quote ("Veni, vidi, vici" in Latin) attributed to Julius Caesar. It consists of three independent clauses, each with a subject ("I") and a verb in the simple past tense ("came," "saw," "conquered"). The clauses are correctly joined by commas, representing a list of actions. This sentence is grammatically correct and a well-known historical saying.
(3) He are walking the dog.
This sentence has a subject-verb agreement error. The subject "He" is singular (third person singular). The verb "are walking" uses the plural form of "to be" ("are"). The correct form would be "He {is} walking the dog."
(4) It is ten for nine.
This is an unusual way to express time. Common ways to express time around 9:00 include:
"It is ten {to} nine" (meaning 8:50).
"It is ten {past} nine" (meaning 9:10).
"Ten for nine" is not standard English for telling time. It might mean something in a very specific, non-standard context, but generally, it's grammatically incorrect or nonsensical for time.
Step 2: Identify the most grammatically correct sentence
Option (2) "I came, I saw, I conquered." is a series of simple, grammatically correct clauses, forming a well-known and correct sentence.
Option (1) is debatable in its precision ("two pants" vs "two pairs of pants").
Option (3) has a clear subject-verb agreement error.
Option (4) is not standard for expressing time.
Therefore, option (2) is the most clearly and unequivocally grammatically correct sentence.