30) ข้อใดเป็นโรคพันธุกรรมที่มีจำนวนโครโมโซมน้อยที่สุด \( \begin{array}{ll}\text { 1. กลุ่มอาการดาวน์ } & \text { 2. กลุ่มอาการคริดูชาต์ } \\ \text { 3. กลุ่มอาการพาทัวซินโดรม } & \text { 4. กลุ่มอาการเทอร์เนอร์ซินดรม }\end{array} \)

B. Write the letter for the correct answer. \( \begin{array}{lll}\text { 1. A vertebra is part of the } \\ \begin{array}{lll}\text { (a) skull } & \text { (b) backbone } & \text { (c) rib cage }\end{array} \\ \begin{array}{lll}\text { 2. The ribs are attached to the }\end{array} \\ \begin{array}{lll}\text { (a) skull } & \text { (b) brain } & \text { (c) backbone }\end{array} \\ \begin{array}{lll}\text { 3. A group of bones that protects the brain is the } \\ \text { (a) skull } & \text { (b) backbone } & \text { (c) rib cage }\end{array} \\ \begin{array}{lll}\text { 4. The backbone is made up of many cords } & \text { (b) ribs } & \text { (c) vertebrae }\end{array}\end{array} \).

Answer True or False. 1. Cartilage is harder than bone. 2. You have the same amount of cartilage in your body all your life. 3. Bones can repair themselves. 4. Red blood cells are made in marrow. 5. Bones always stay the same size. 6. Some cartilage changes to bone.

C. Answer the questions. 1. What is the important job of the rib cage? 2. What are the bones of the backbone called? 3. Name the important job of the skull. 4. What could happen if your spinal cord were injured? 5. What is the important job of the backbone?

The part of the skeleton that protects the spinal cord is the \( \begin{array}{lll}\text { (a) rib cage } & \text { (b) skull } & \text { (c) backbone } \\ \text { The } & \text { is the part of the skeleton that protects the heart. } \\ \begin{array}{lll}\text { (a) skull } & \text { (b) rib cage } & \text { (c) backbone }\end{array}\end{array} \)

D. Answer the questions. 1. What tissues hold bones together? 2. How do hinge joints work? 3. What kind of joint can move in a complete circle?