Question

part a
which is a central idea of the text?
ancient lakes are important historically, biologically, and economically, but they face many threats.
there will be a loss of biodiversity in ancient lakes unless scientists can figure out how to add the right nutrients to the water.
ancient lakes are critical to the tourism industry, so the industry is leading the fight to save them from losing their biodiversity.
humans need to limit their interactions with ancient lakes, or they will disappear entirely.

Explanation:

The first option encompasses the historical, biological, and economic importance of ancient lakes along with the threats they face, which is a comprehensive central - idea. The second option focuses only on biodiversity and nutrient addition. The third option emphasizes tourism industry's role which is not the main idea. The fourth option is about limiting human interactions, which is also not the over - arching central idea.

Answer:

Ancient lakes are important historically, biologically, and economically, but they face many threats.