To estimate the quotient of 48.6 divided by 0.7, we can round both numbers to make the division easier.
Rounding 48.6 to the nearest ten gives us 50 and rounding 0.7 to the nearest whole number gives us 1.
Thus, the best expression to use for estimation is:
50 divided by 1.
However, if we strictly look at the given options, "50 divided by 1" is indeed the most appropriate choice.