1. The correct answer is A. theme.
Theme of a novel or other literary work is the main idea - what the writer wants us to understand and remember after we've finished reading it. It is usually something short, and true, which is why in the literary world the theme is also known as short truth.
2. The correct answer is B. Love is blind.
This is not a topic found in The Call of the Wild, whereas primitive instincts rising to the surface, as well as survival of the fittest do. The novel is about a partially domesticated dog whose wild instincts are kicking in so he has to decide what to do next.
3. The correct answer is C. solidarity.
The word solidarity means unity, agreement - and it is evident in a sports team which has won a game. Exertion means a struggle, a lot of effort; the word heredity relates to genetics, passing down genes from parent to offspring, so neither of those two options are correct.