Because the sand is durable and resistant to external environment changes and difficult conditions. Therefore, it does not affect the fifo and contains restricted areas.
Because sand is durable and resistant to external environmental conditions and climate change can be difficult. So fifo does not affect use and consists of a limited space.
Because the sand is durable and resistant to the external environment and the state change is difficult. So FIFO therefore does not affect the use and comprising an area is limited.