Answer :
It is definitely clarity! If you are not clear you will not be understood, therefore when making a business deal you wont be able to get your point across. and getting your point cross is key to a successful business deal. Hope I was able to help. :)
Some of the characteristics of a good business letter are accuracy, clarity, and brevity in that order. Letters must be accurate in the information that is being portrayed. They must also be clear so that the reader fully understands the message that is attempting to be conveyed. And finally they must be concise of brief so that the reader can obtain the information quickly and clearly.