Rift valleys can form when fractures in Earth's crust widen. The valley walls slowly move apart at a rate of only a few millimeters a year. Which type of boundary would rift valleys form at?
A. Convergent
B. Divergent
C. Transform
D. Transform Fault

B. Divergent

Explanation:

Rift valleys are usually formed at divergent margins where fractures in the earth's crust widens.

The fracture widens due the pulling apart of the plates that are involved.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.