The sentences "The dog chased the cat" and "The cat chased the dog" mean different things even though they contain the same words. This is because of .

Syntax.

Explanation:

What Syntax studies is the principles and processes of sentences in a particular language, including the word order. In this case, the sentences "The dog chased the cat" and "The cat chased the dog" mean different things because of the word order: The dog chased the cat means that the dog was running behind the cat, after him. If the cat chased the dog, the opposite. In this simple example we notice the importance of syntax and the word order in a sentence. It's not the same if we say "The man was helped by the medic" rather than "The medic was helped by the man" even if it shares the exact same words.

hygrometers and hair thermometers (often found as part of hygrometers/psychrometers) can be used to measure humidity. barometers are used to measure atmospheric pressure, while anemometers are used to measure wind speed. so the 2nd and 4th choices should be the correct answers.