Will you check the following English sentences?

1. Paying attention to the intonation mark, listen carefully. (Do I have to use 'mark'?)

2. Put your tongue between your upper teeth and lower teeth, and say th by letting the air over your tongue abruptly.

3. If the question has a rising intonation, mark an upward arrow, if it has a falling intonation, mark a downward arrow in the parentheses.

4, Blow out the candles on the birthday cake. He is trying to blow out the candles on the cake. (candles or candlelights?)

5. Do you have any brothers or sisters?
No, I don't. I am an only child./ I am the only child./ I am an only son. / I am an only daughter. (Which expressions are right?)

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I have posted sentences. Would you check whether they are grammatical or not. I'd like to use correct English expressions.

#1 No, you do not need mark there.

#2 The "th" is an elongated sound, so you do not need the word abruptly. Use the word "blowing" instead of "letting".
#3, Put a semicolon after arrow.
#4. Candles is correct.
#5. The first two of those would be correct ways to answer that question.

Sure! I can help you with that. Let's go through each sentence and address your questions.

1. "Paying attention to the intonation mark, listen carefully." (Do I have to use 'mark'?)
Yes, in this sentence, it is correct to use the word "mark" after "intonation." It specifies that you should pay attention to the specific marks used to indicate intonation in the sentence. The word "mark" refers to the punctuation marks used, such as question marks or exclamation marks.

2. "Put your tongue between your upper teeth and lower teeth, and say th by letting the air over your tongue abruptly."
This sentence seems grammatically correct. It provides clear instructions on how to produce the "th" sound. However, it might be clearer if you specify that the air should be released by gently blowing it out over your tongue.

3. "If the question has a rising intonation, mark an upward arrow; if it has a falling intonation, mark a downward arrow in the parentheses."
This sentence is grammatically correct and clear in its instructions. It explains how to mark the appropriate arrows in parentheses based on the intonation of a question.

4. "Blow out the candles on the birthday cake. He is trying to blow out the candles on the cake." (candles or candlelights?)
Both "candles" and "candlelights" are correct in this context. The word "candles" refers to the objects themselves, while "candlelights" could be used to describe the light emitted by the candles. However, since you are referring to extinguishing the flames, using the word "candles" is more appropriate.

5. "Do you have any brothers or sisters? No, I don't. I am an only child./ I am the only child./ I am an only son./ I am an only daughter." (Which expressions are right?)
All of the expressions you provided are grammatically correct. However, the most commonly used expressions are "I am an only child" or "I am the only child." These phrases imply that you do not have any siblings. The expressions "I am an only son" or "I am an only daughter" specifically indicate that you are the only son or daughter in your family.

I hope this helps! Let me know if you have any further questions.