What is the greatest possible length which can be used to measure exactly the lengths 12 m, 6 m and 40 m?	Choices:
A) 2m
B) 5m
C) 3m
D) 10 m
E) 20 m
Required length = HCF of 12 m, 6 m, 40m = 2m   2mnswer is 2m
<result>A</result>
What is the greatest possible length which can be used to measure exactly the lengths 12 m, 6 m and 40 m?