According to the author, what’s the main reason for the failures of most enterprises

A．The high temperatures required for its use.
B．The high cost of materials used in its production.
C．The lack of trained environmental engineers.
D．The opposition of automobile manufacturers.

A．Wars or natural disasters make them lose their families.
B．They want to help their families earn enough,mooney to survive.
C．They are poor.
D．All the above.