Question

look at these details from a paragraph about swimming. swimming can help your legs become stronger. swimming can strengthen your heart. swimming can help keep your lungs healthy. choose the main, or central, idea that ties all the details together. swimming makes your heart and lungs strong. swimming is good for your body. diving into water is a hard skill to master.

Explanation:

The details mention benefits of swimming for legs, heart and lungs. The first option only focuses on heart and lungs, the third is about diving which is not related to the given benefits. The second option, "Swimming is good for your body", encompasses all the given benefits.

Answer:

Swimming is good for your body.