It is mentioned in the passage "they spend the day socializing, exploring their indoor or outdoor enclosures. They also regularly engage in games with researchers." . This indicates that the orangutans are friendly: words like 'socializing', engaging in games with researchers, all resonate more with 'friendly' than with 'energetic'. Hence the former is a more suitable option than the latter. The latter is not supported by the passage at all. It might be confusing because "... add up to the same level of exercise performed by humans in physically demanding agricultural lifestyles" refers to energy levels, but it isn't the same as 'energetic', the latter referring to a high energy level. But, high energy levels are not indicated here. Hence option B is correct and D is incorrect. Options A and C are incorrect because "low energy throughout means less energy is available to do things like grow and reproduce" does not make them slow or lazy. Their growth is slow, but they are not slow on the whole. The line "spend the day socializing, exploring their indoor or outdoor enclosures" negates the words 'slow' and 'lazy'.