What do geologist call the “Ring of fire”

Relatively steep zone that is compared with the shelf that marks the boundary between continental crust and ocean crust.

Brian's school locker has a three-digit combination lock that can be set using the numbers 5 to 9 (including 5 and 9), without repeating a number. the probability that the locker code begins with a prime number is %. the probability that the last digit of the locker code is an odd number is %.

Which of the following areas has the highest population density?