Which of the following is a product of volcanicity?

A plug dome is a product of volcanicity. It is formed when magma that is rich in gas is squeezed out of a volcano and solidifies near the vent. The gas bubbles inside the magma cause it to be more viscous and sticky, which makes it pile up into a dome-shaped plug. As more magma is forced up from below, the plug can grow larger and larger until it eventually explodes, releasing ash, gas, and other volcanic materials. Plug domes are common features of stratovolcanoes, which are tall and steep volcanoes that are built up over time by successive eruptions of lava, ash, and other volcanic materials.