Answer: Option C
The inverse ratio of a set of numbers refers to the reciprocal of each of the numbers in the set. The reciprocal of a number is defined as 1 divided by the number.
For the ratio 3 : 2 : 1, the inverse ratio can be calculated as follows:

• The reciprocal of 3 is 1/3
• The reciprocal of 2 is 1/2
• The reciprocal of 1 is 1
• So the inverse ratio is 1/3 : 1/2 : 1

In a ratio, the order of the numbers is important. So the inverse ratio is not the same as the original ratio.
It's also worth noting that the inverse ratio does not necessarily have the same meaning as the original ratio. For example, if the original ratio represents the proportions of different ingredients in a recipe, the inverse ratio may not make sense in the same context.
So, the correct answer is option C (2 : 3 : 6).
To summarize:

• The inverse ratio of a set of numbers is the reciprocal of each number in the set.
• The inverse ratio does not necessarily have the same meaning as the original ratio.
• The answer to the given question is option C (2 : 3 : 6).