Hello. You did not show what were the themes of the unit to which the question refers, which may leave the answer a little inaccurate.
Two recurring themes in transcendentralistic music is the human capacity to live a rural life. This type of theme is widely found in country music, where nature and country life is portrayed as the ideal life, due to the hard work environment, but rewarding and the presence of nature that makes life lighter and more beautiful. Another recurring theme is the happiness of being loved by someone and how it affects the human being in a positive, magical and playful way, leaving life beautiful and decreasing the perception of problems that may arise.
These themes are completely centered on transcendentralism, which promotes the intimate relationship between the human being, his self, society and the environment. As these are very common themes, I feel influenced to talk about them, because they are also the themes that present a greater symbolism for me.
The answer is B, because the eclipse allows scientists to study the sun, a very rare treat
By explaining problems and giving solutions! this is the best fit because the other two might make sense at a first glance, but only explaining problems and solutions would be an effective way to teach people how to set up an aquarium by giving them examples of what to do and what not to do whereas the others are just him talking about his aquarium.