Firstly, this question is very dumb. Secondly, there was your sentence :)
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Firstly, I would have to think about your question, which seems a perfectly sensible question to me. Having thought about the question I would firstly suggest there are many sentences which could contain the word firstly, but these should do for now.
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you say first, because firstly is not a word
I can give you a sentence using the word galaxy.
Can you give me a sentence with the word betwitched?
Firstly I will write a small sentence. There are two reasons for this decision: firstly small sentences are easier to understand and secondly they are easier to think of.
Firstly, we need to gather all the necessary information before we can proceed with the project.
yes. can u give me a sentence with the word headline
Can you give sentence by using abyss word?
The sentence with the word 'why': Why do you ask this question?
Yes, I can give you a sentence with the word obituary. (I just did! ahahahaha)
Give me a sentence on word brood
In the sentence 'Can you give a definition for that word?', YOU is the subject.
Give me a sentence using the word Kerchief. That is a sentence that uses the word. Seems as though you could figure this out.