Where should a hyphen(s) be added in the following sentence:
One researcher at DePaul University has studied how personality traits may affect an astronaut's suitability for a long term mission to Mars.


A- One researcher at DePaul University has studied how personality traits may affect an astronaut's suitability for a long-term-mission to Mars.


B- No hyphens are needed


C- One researcher at DePaul University has studied how personality-traits may affect an astronaut's suitability for a long term mission to Mars.


D- One researcher at DePaul University has studied how personality traits may affect an astronaut's suitability for a long-term mission to Mars.