Question

corals have a wide distribution in the worlds oceans, but the reef - builders that form reefs typically are restricted to relatively warm tropical waters between 30° north and south latitudes. clean, clear water with the right amount of nutrients is essential to their health. after initial colonization of a hard substrate and given suitable conditions for coral growth, an individual larval spatfall gives rise to a colony. given enough time, coral colonies become thickets. as coral thickets build upward on the skeletal remains of older colonies, a reef is established. today, richly diverse coral reefs are found along tropical coastlines, on the margins of volcanic islands, and as isolated coral atolls. coral reefs are dynamic, evolving through time into different forms... volcanic islands subside; that is, they have a tendency to cool, condense, and sink through time. as they subside, tropical coral reefs grow upward along their margins. this sentence is, as coral thickets build upward, a reef is established. (paragraph 2) what is the main role of this sentence in the passage? 1. to show that coral reefs are fragile 2. to show how coral reefs start to develop 3. to show that coral reefs constantly change 4. to show how coral reefs are like other coral forms

Explanation:

The sentence "As coral thickets build upward, the skeletal remains of older colonies, a reef is established" describes the process by which coral reefs start to form. It details how the accumulation of skeletal remains from older colonies as the coral thickets grow leads to the establishment of a reef, which is about the development process of coral reefs.

Answer:

1. to show how coral reefs start to develop