Drink lots of water, take breaks in the shade
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Answer: 3 - infrared light</h2>
Explanation:
<u>There are certain areas of the Milky Way that cannot be observed using the visible range of the electromagnetic spectrum</u> (this includes blue light and red light). This is because these areas are covered or hidden behind columns of interstellar dust and dark matter.
However, using infrared light and sometimes radio waves, it is possible to observe the galaxy better, because this light manages to pass through all that interstellar dust.
My guess is A. depth increases because I know that the deeper you go in the ocean, the higher the water pressure is (which makes it difficult to explore).