Notice that each member of the crew resurfaced 1/8 of a mile of the road.
Then in between the 6 members they did a total of :
6 * 1/8 of a mile = 6/8 of a mile = 3/4 of a mile.
We simplified a common factor "2" in numerator an in denominator to reduce the fraction to 3/4.
So, please select answer D in your list of options.