Final answer:
At divergent tectonic plate boundaries, features often seen include new ocean ridges and seafloor mountains. Basaltic lava, which is low in silica and flows easily, is typically associated with the formation of shield volcanoes in these areas. option (B)
Step-by-step explanation:
When tectonic plates move apart, a feature you usually see is new ocean ridges and seafloor mountains. This occurs because the mantle below experiences reduced pressure, leading to the creation of magma. New basaltic material from the mantle rises to fill the gap between the plates, forming the characteristic mid-ocean ridges and seafloor spreading centers like the Mid-Atlantic Ridge. Therefore, the correct answer is 'a) New ocean ridges and seafloor mountains'.
As for the second part of the question regarding the type of magma that is low in silica, flows easily, and tends to form shield volcanoes, the answer is Basaltic lava. This type of lava is typically found at divergent boundaries where new oceanic crust is formed.