Identify the sentence that contains a grammatical error.

The sentence "He know that the game starts at six" contains a grammatical error due to the incorrect subject-verb agreement. The subject "He" is singular, and therefore it should be paired with the singular form of the verb "to know," which is "knows." Hence, the correct form should be "He knows that the game starts at six." Ensuring that subjects and verbs agree in number is a fundamental rule in English grammar, which helps maintain clarity and correctness in writing. The other sentences correctly demonstrate proper subject-verb agreement and are grammatically sound.