Which of the following statements concerning the different types of volcanic risks is FALSE?单项选择题

Although lahars can be deadly, because of their greater speeds pyroclastic flows pose much more of threat to populations at a distance.

Despite centuries of quiet, a volcano is never truly ‘extinct’ until it is no longer associated with any source of magma generation.

Despite a common fear of suffocating during a volcanic eruption, most eruption victims are killed by deadly pyroclastic flows or lahars.

Pyroclastic flows are usually associated with volcanic eruptions of water-rich magmas that have intermediate or high silica contents.

If an eruption is violent enough to send ash and gas aerosols high into the stratosphere, they can spread across more of the Earth.