Answer
The best estimate for a person's weight is: a. 60 kg.
Work Step by Step
60 g and 60 dag are both less than 1 kg, so these choices are clearly too light for the weight of a human.
A weight of 60 kg is the weight of six 10-kg sacks of potatoes which seems like a reasonable estimate for the weight of a person.
The best estimate for a person's weight is: a. 60 kg.