Which of the following is the best opening sentence for a business letter that you want to sound fairly informal?

A. I am in receipt of your order of February 10.
B. This letter is to make you cognizant of our receipt of your order.
C. Your order of February 10 arrived in our office today.
D. Please be advised that I've just received your order.

The point is -- which one do YOU THINK is appropriate for an informal tone?

Let us know what YOU THINK, and we'll be happy to comment.

The best opening sentence for a business letter that you want to sound fairly informal is option C: "Your order of February 10 arrived in our office today."

To determine the best opening sentence, it is important to consider the level of formality and clarity of the sentence. In this case, option C conveys the receipt of the order while using more direct and informal language. The sentence clearly states the date of the order and indicates that it has just arrived in the office. This opening sentence sets a friendly and approachable tone for the rest of the letter.