The sentence emphasizes the discovery of new, undocumented species, which relates to the difficulty and delicacy of studying deep-sea environments. The word precarity means the state of being uncertain, insecure, or dangerously liable to fall or collapse; this is the most sophisticated and accurate synonym for fragility in the context of sensitive, easily disturbed ecosystems. While options like abyss (depth) and immense (vastness) describe the physical size of the deep sea, only precarity captures the focus of the research on the delicate and vulnerable nature of these unique biological systems.

The word judicious is the correct choice. It means showing good judgment or sense, which perfectly describes the careful and skillful selection of colors necessary to achieve a "stunning visual effect" that successfully draws a viewer's attention. The other options—capricious (erratic/unpredictable), improvident (wasteful/lacking foresight), and promiscuous (unselective)—all imply a lack of thought or control, which would contradict the successful and impressive outcome described in the sentence.

The paragraph describes the Amazon rainforest as being home to "countless species that are found nowhere else on Earth," which clearly indicates an extremely rich and vast variety of life. The word "abundant" means plentiful or existing in large quantities, making it the most accurate descriptor for the rainforest's biodiversity. The options "sparse" (thinly dispersed) and "negligible" (insignificant) directly contradict the known fact and the supporting context of countless unique species. "Redundant" (unnecessary repetition) is irrelevant to the context of biological variety.

The correct choice is insurmountable. This adjective means impossible to overcome, which accurately conveys the overwhelming difficulty of navigating a dense forest with towering trees and thick undergrowth. The forest is clearly described as posing a significant hurdle. Options like "trivial" (insignificant), "effortless" (easy), and "mundane" (ordinary or dull) are inappropriate because they directly contradict the context of the environment presenting a substantial challenge to the explorers.

The word monotonous describes something that is dull, tedious, and repetitive because it lacks variety or change. The most precise synonym that captures this meaning is tedious. Other strong alternatives include boring, dull, or humdrum, all of which convey a feeling of weariness or lack of interest resulting from an unvarying routine or activity.

The blank requires an adjective that describes the orangutan's intelligence as remarkable and capable of complex tasks like solving puzzles and using tools. The term "extraordinary" perfectly fits this context as it means remarkable or exceptional. The other options, "rudimentary" and "primitive" (meaning basic or simple), or "insubstantial" (meaning lacking strength or importance), contradict the evidence of advanced problem-solving and tool use. Therefore, extraordinary is the correct choice.

The sentence describes the psychological tendency (inclination) for people to match (conform) their behavior with social norms. An inclination is a strong preference or natural drive, which precisely fits the idea of a powerful force causing individuals to adjust their actions.

The Blue Economy is centered on the sustainable use and conservation of ocean resources for economic growth, improved livelihoods, and ocean ecosystem health. The correct terms, conserving and degradation (Answer C), fit this concept because the goal is to emphasize the importance of protecting or preserving ("conserving") ocean resources while simultaneously ensuring that the resulting economic activities do not lead to the deterioration or damage ("degradation") of the marine environment. Terms like depleting or exploiting contradict the core principle of sustainability, and the aim is to prevent degradation rather than just restore it.

The sentence emphasizes the stealth capabilities of the submarine. "Complete" indicates total invisibility to detection systems, and "streamlined" refers to the efficient, sleek design that allows the submarine to remain submerged for long periods while avoiding detection.

The word "Acrimony" refers to bitterness and hostility, which accurately reflects the emotional response to the devastation caused by ethnic slaughter. "Detriment" suggests harm or damage, in this case, to the social structure and relationships within the community. The sentence illustrates the long-lasting negative impact of such violence on social cohesion.