A) Round 3.12 to one decimal place.

3.10

Step-by-step explanation:

this is because

if the last digit is more than five it will be rounded up

if it is lower than five then it will be rounded down.

eg.

23

will be rounded to 20 as the last digit is 3 so which is less than five.

eg. 47

will be rounded to 50 as the last digit is 7

so which is more than five.

EVEN if the last digit is 5 then it is also round up.

eg. 85

will be rounded to 90 as the last digit is 5

so which is equal or more than five

The answer is 3.1 because 2 is lower than 5 so it rounds down