The answer will depend on the degree to which the number is rounded. Without any indication of that, it is not possible to answer the question sensibly.
To the nearest whole number, 1
12, because if you rounded to the tenths spot you get 12
11.7 billion rounded to the nearest 10 billion would be 12 billion.
12 Hours and 12 minutes rounded to the nearest hour is 12 hours.
12
12
12.0107 rounded to the nearest whole number is 12.
11.7 billion rounded to the nearest 10 billion would be 12 billion.
Rounded to the nearest whole number it is 12
12, because if you rounded to the tenths spot you get 12
10
12 Hours and 12 minutes rounded to the nearest hour is 12 hours.
12 is an integer and so already rounded to a hundredths (and more).
12
12
Rounded to the nearest whole number it is 12
If rounded to a whole number, it would be rounded to 8.
sqrt(12) = ±3.4641 (rounded)