* Intrusive igneous bodies are formed when magma cools and solidifies beneath the Earth's surface.

* Batholiths are the largest type of intrusive igneous bodies. They are massive, irregularly shaped, and often form the cores of mountain ranges.

Let's look at the other options:

* Pyroclast refers to fragments of volcanic rock and ash ejected during an eruption. They are extrusive features, not intrusive.

* Lava flow is the molten rock that erupts onto the Earth's surface. It is also extrusive.

* Lahar is a type of mudflow associated with volcanic eruptions, making it extrusive.

Therefore, only Batholith is an intrusive igneous body.