To my knowledge, the correct answer among all of the given choices is C.) Steam. If I'm not mistaken, this was the time that more trains came into use.
I hope this is the answer you were looking for and that it helps!! :)
"Now Enkai lives at the top of Mount Kenya, and we Maasai still live below, herding cattle down in the plains. <span>It’s not a bad life, especially when Enkai is the Black God, providing for us."
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D I took this test and I believe this was it