Allows the endodermal cells to regulate the amount of water flowing into the xylem.

The correct answer will be casparian strips.

Explanation:

The Casparian strip is a  look like a ring, of evident parts of the endodermal cell walls in roots, which regulate water and minerals to pass from the semipermeable plasma membrane of such cells instead of their cell walls.

When water from the root epidermis and finally reaches the endodermis, they met the Casparian strip. As it is an impermeable membrane in the cell wall, it blocks materials from passing through it, so stops the apoplastic pathway and forces all material to pass through the cytoplasm. This is very essential because only the plasma membrane can control the amount and type of substances passing through the membrane, but the cell wall cannot. So, the Casparian strip allows the plant to regulate how much minerals and water it absorbs from the soil.

Thus, the correct answer will be casparian strips.

1 and 6 for apex

the answer to your question is:

c. complementary base-pairing