Use process of elimination. From what you gave me to read, you can cross off competition. A drought killed the plants and not competition to live. Go down the list of words and look up the definition. Look at nudation and ecesis later because they are different words that may or may not be challenging to understand. You know what reaction and migration is without looking it up. Once you cross off all words answers that don't match up, ask yourself, which remaining answer goes? Nudation is basically new plants that have successfully started growing after a huge environmental change. Ecesis is sort of similar however, the establishment in a new habitat or environment is not from a big change. Therefore, nudation is the correct answer.
The answer would be e. it would have released water in a volcanic outgassing. The planets were hot to have gas from the solar nebula. Earth,Mars as well as Venus then created their atmosphere through volcanic eruption and retain gases from comet and icy planetesimals vaporizing.
When the plates move,collide, or get farther apart this causes earthquakes due to the tectonic movement. Then due to the force of the earthquake if the plate movement and the earthquake happened under water can cause a tsunami. When two plates meet are are equal density they push up to form mountains of there is a pocket of magma then a volcano may form
