To solve this problem, we need to analyze the statements regarding the formation of annual rings in trees:$\newline \bullet$Option 1: Annual ring is a combination of spring wood and autumn wood produced in a year.$\newline$ - This statement is true. Annual rings are formed due to the seasonal activity of the cambium.$\newline$ - Spring wood (or early wood) is formed during the growing season when the cambium is highly active, producing larger cells.$\newline$ - Autumn wood (or late wood) is formed when the cambium is less active, producing smaller, denser cells.$\newline \bullet$Option 2: Differential activity of cambium causes light and dark bands of tissue early and late wood respectively.$\newline$ - This statement is true. The difference in cell size and density between spring wood and autumn wood creates visible light and dark bands.$\newline \bullet$Option 3: Activity of cambium depends upon variation in climate.$\newline$ - This statement is true. The cambium's activity is influenced by climatic conditions, such as temperature and rainfall, leading to the formation of distinct annual rings.$\newline \bullet$Option 4: Annual rings are not prominent in trees of the temperate region.$\newline$ - This statement is not true. In fact, annual rings are most prominent in trees of the temperate region due to the distinct seasonal variations that affect cambial activity.$\newline$Therefore, the correct answer is Option 4, as it is the statement that is not true about the formation of annual rings in trees.