Question

how can families best achieve a positive effect on physical health?
by taking walks together
by going shopping together
by attending church together
by watching movies together

Explanation:

散步（taking walks）是一种身体活动，有助于增强体质、促进血液循环等，对身体健康有积极影响。而一起购物（going shopping）、一起去教堂（attending church）、一起看电影（watching movies）更多是社交或精神层面的活动，对身体健康的直接积极影响相对较小。

Answer:

by taking walks together