Chapter 1. Star
Unit 1. Changing Stars
Unit 2. Twinke, Twinkle, Little Star
Unit 3. The Hubble Space Telescope
Unit 4. The Oldest Observatory in Asia
Chapter 2. Plants
Unit 1. Different Areas, Different Plants
Unit 2. Plants Make Their Own Food
Unit 3. Water Lilies
Unit 4. Numbers in Nature
Chapter 3. Relationships
Unit 1. We Live Together
Unit 2. Food Chains and Food Webs
Unit 3. Good Relationships through Sports
Unit 4. Three Friends: Gram, Kilogram, and Ton
