Please help me with D I don't understand

The earth's internal process which drives seafloor spreading is

There is only one climate type in motion across the world at a time

The incident command system (ics) is: a. most applicable to the management of complex incidents that extend over many hours or days. b. a military system used in domestic incidents to ensure command and control of federal resources. c. a standardized management tool for meeting the demands of small or large emergency or nonemergency situations. d. a relatively new approach created based on the lessons learned from hurricane harvey disaster operations.