Large-scale environmental catastrophes . A. Result from human activities b. Have a negative impact on ecosystems c. Affect a variety of environmental factors d. All of the above.

According to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does maria's voyage take according to samir?