Final answer:
In the examples given, only 'the Grand Canyon' should be capitalized, as it is a proper noun, while the phrases 'a white house' and 'the train station' should be written in lowercase unless referring to specific, named entities.
Step-by-step explanation:
In English grammar and punctuation, capitalization rules are important to understand for proper writing. You've presented three different phrases: 'a white house', 'the train station', and 'the grand canyon'.
For option A: The phrase 'a white house' does not need capitalization unless 'White House' is being used to refer to the official residence of the President of the United States. In this case, because it is not specified if this is the official residence, it should be written in lowercase.
For option B: Similarly, 'the train station' is a common noun and does not require capitalization unless it is part of a proper noun, such as the name of a specific train station (e.g., 'Grand Central Station').
For option C: 'The Grand Canyon' is indeed a proper noun as it is the name of a specific place, a notable landmark. Therefore, it should be capitalized to read as 'The Grand Canyon'.
Based on these explanations, only option C should be capitalized because it is a proper noun referring to a famous geographical feature.