A type of buyer in an acquisition that is primarily interested ... A business agreement between two different companies to work ... A measure of the amount of operating cash flow needed to meet ... A type of debt instrument used in a particular type of short-term ...
The temperature of the Exosphere ranges from 300 degrees Celsius to 1700 degrees Celsius.
You can read in wikipedia that in planets with substantial atmposphere, the exosphere is the uppermost layer of the atmosphere where it merges with the interplanetary space (credit to wikipedia). Then c. is the right option.