So, what is the case in which he uses the least coins? can he use 1 coin? no, there isn't a 35 cent coin. can he use 2 coins? yes! he can use 25+10 cent coins!
now, the largest number of coins means the coins of the smallest value: so using only 5 cent coins. How many would this be?
It could be A or B because them stepping on a rock could cause the rock to crack and another could come along and do the same thing and the rock would eventually break.
