Since misery and depression are both sad/bad kinds of feelings, then we have to find a pair of words that have the same kind of feeling in order to complete this analogy. The correct answer should be melancholy and boredom.
The simple machine that is a shovel is a lever
Given that Carla has already knowledge of the example from the Ecology textbook, then her reading will increase. It is called a prereading, it is a technique in which the reader will skim the text before reading it thoroughly.
Carla already has an idea on what she will be ready since she has come across the example before reading the text carefully.
