If the following events were placed in chronological order, which would come fourth?

The answer is D. Eggs excreted in faeces or urine hatch out in fresh water (E) and release miracidia which invade snails; cercaria are released from the snail (B) and invade human skin (C) losing their tails. The larvae invades vessels, reaches the liver and enters the portal circulation (D) where it matures and the adults migrate to i.e., the perivesical veins (A). The adults lay eggs which are excreted by the host.