Lipids, also known as fats, play multiple roles in the body. Fats are broken down in the digestive tract to form individual fatty acids and cholesterol molecules. <span>Carbohydrates are the preferred source of energy for most of the tissues in the body, including the nervous system and the heart</span>
        
             
        
        
        
Stem cells arise from the inner mass of the cell
Signalling factors trigger differentiation in stem cells
Genes that lead to the production of undifferentiated blood cells are activated
Signalling factors cause undifferentiated blood cells to produce red blood cells
Explanation:
Red blood cells are formed in the bone marrow. The precursor to the RBC is stem cell which is undifferentiated and pluripotent. The stem cell gets differentiated to form immature RBCs. Immature RBC then gets divided and becomes mature. Stem cell giving rise to RBC is called Haemoctytoblast. The process of erythropoiesis takes 2 days to form new  red blood cells
 
        
             
        
        
        
Explanation:
True, if sedimentary rock is exposed to energy from the sun at Earth's surface for a long enough time, it can melt into liquid rock and form igneous rock. No, igneous rock forms under Earth's outer layer due to energy from Earth's interior, but sedimentary rock is only at Earth's surface.