The proper way to write a single digit whole number in a sentence is

Numbers should be written in full when it is necessary to put them in a text.

Explanation:

The correct way to write an integer of a digit in a sentence is to write it by completely using letters. This is usually correct, except when this number refers to dates or percentages. However, as an integer you must write it in full. For example: Let's say you have two pet cats and want to write a note telling your mom what time cats should eat. The correct would be to write "The two cats should eat every half hour" The incorrect would be to write "The 2 cats should eat every half hour".

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explanation:

answer is b "guaranteed the safety of any merchant"

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