Answer: Option C. +/-3
Solution:
The error range is most reliable if the width of the range is smaller:
Width=w=2 Absolute value (error range)
A.) w=2 Absolute value (+/-12)=2(12)→w=24
B.) w=2 Absolute value (+/-6)=2(6)→w=12
C.) w=2 Absolute value (+/-3)=2(3)→w=3
D.) w=2 Absolute value (+/-9)=2(9)→w=18
The smallest width is in option C.
