Question

choose two key details to create a summary of the text.
mid-ocean ridges spread at different rates, leading to different physical features.
mid-ocean ridges occur at divergent plate boundaries, where there is major volcanic activity.
the mid-ocean ridge system is earth’s biggest mountain chain, although the vast majority is underwater.
the mid-ocean ridge system remains mysterious, since only a tiny fraction has been explored.

Explanation:

To solve this, we analyze the text's focus on mid - ocean ridges (size, underwater extent) and the options:

1. Option 1 talks about different rates and physical features, not the main summary point.
2. Option 2 focuses on plate boundaries, not the key summary aspect.
3. Option 3: The text emphasizes the mid - ocean ridge system as Earth’s biggest mountain chain with most underwater (e.g., “the mid - ocean ridge system is Earth’s biggest... majority is underwater”). This matches the core idea.
4. Option 4 is about mystery/exploration, not the main summary from the text.

La opción correcta se basa en el enfoque del texto sobre el sistema de crestas mediooceánicas como la mayor cadena montañosa de la Tierra, con la mayoría sumergida. Otras opciones no capturan este punto central.

Answer:

1. The mid - ocean ridge system is Earth’s biggest mountain chain, although the vast majority is underwater.