What is the register of the following sentence?

My relatives stayed at your hotel last year and they were delighted by the experience.

What is the register of the following sentence?

I totally understand that six months abroad will not be easy for our department.

What is the register of the following sentence?

I kindly ask you to assist me in this venture, as I am certain a word from you should grant me the attention of Mr Belmont, our CEO.

What is the register of the following sentence?

I have been studying Spanish for four years now and getting ready for this possible dream.

What is the register of the following sentence?

I'm writing to tell you that I miss you and that I totally loved the present you sent me.

What is the register of the following sentence?

Researchers carried out a survey in regard to the epidemic.

What is the register of the following sentence?

I believe he has poor taste in all things decor.

What is the register of the following sentence?

My boss dislikes small talk.

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I'm sick of having to listen to his loud music all night long; I just can't study with all the noise.

What is the register of the following sentence?

I would like to point out that listening to such loud music through the night is simply unacceptable.

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It would be a great opportunity for our branch to collaborate in a number of projects together.

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To make matters worse, the staff were extremely impolite.

What is the register of the following sentence?

How are you? I hope this letter finds you well. I's been so long since I last saw you...

What is the register of the following sentence?

Sorry, it has taken me so long to write back and thank you.