In Tim O'Brien's "Ambush," which element directly enhances the theme of the past's imprint on the present?

Ithink that the missing word is mixed

Ithink the answer is either a , c or d

Temperature, rainfall and relative humidity.

The reason why i feel that the theory of plate tectonics is correct because scientists have found dinosaur bones of the same species in africa, asia, and in the americas. which means that they must have been together at one point in time. plate tectonics is also how the hawaiian islands were formed. as the plate hawaii is on was moving north west, magma would melt through the sea bottom and hardening. forming into the island chain. plate tectonics also explains the mariana trench. two plates were moving away from each other and made a giant crack in the ocean floor running 2,550 kilometers (1,500 miles)  long.