To solve this problem, we need to identify where Casparian strips occur. Let's analyze each option:$\newline \bullet$Option 1: Cortex$\newline$ - The cortex is the layer of cells between the epidermis and the vascular tissue in plants.$\newline$ - Casparian strips are not found in the cortex.$\newline \bullet$Option 2: Pericycle$\newline$ - The pericycle is a layer of cells just inside the endodermis and is involved in the formation of lateral roots.$\newline$ - Casparian strips are not found in the pericycle.$\newline \bullet$Option 3: Epidermis$\newline$ - The epidermis is the outermost layer of cells in plants, providing protection.$\newline$ - Casparian strips are not found in the epidermis.$\newline \bullet$Option 4: Endodermis$\newline$ - The endodermis is the innermost layer of the cortex in plant roots.$\newline$ - Casparian strips are bands of cell wall material found in the endodermis. They are made of suberin and lignin, and they regulate the flow of water and nutrients into the vascular system.$\newline$ - Therefore, Casparian strips occur in the endodermis.$\newline$Hence, the correct option is Option 4: Endodermis.