4) If an oceanic plate and a continental plate collide, the dense ocean plate sinks, or is subducted,
beneath the continental plate. Which of these is formed when the subducted plate melts?
A. Folded mountains and glaciers
B. Magma and volcanic mountains
C. Earthquakes and volcanoes
D. New seafloor and sediments

B. Magma and volcanic mountains.

When continental and oceanic plates collide, the thinner and more dense oceanic plate is overridden by the thicker and less dense continental plate. The oceanic plate is forced down into the mantle in a process known as "subduction." As the oceanic plate descends, it is forced into higher temperature environments. At a depth of about 100 miles (160 km), materials in the subducting plate begin to approach their melting temperatures and a process of partial melting begins.

This partial melting produces magma chambers above the subducting oceanic plate. These magma chambers are less dense than the surrounding mantle materials and are buoyant. The buoyant magma chambers begin a slow ascent through the overlying materials, melting and fracturing their way upwards. The size and depth of these magma chambers can be determined by mapping the earthquake activity around them. If a magma chamber rises to the surface without solidifying, the magma will break through in the form of a volcanic eruption.

So your answer is B.

plz mark brainliest if this helped. :)