Consider the following :1.Pyroclastic debris2.Ash and dust3.Nitrogen compounds4.Sulphur compoundsHow many of the above are products of volcanic eruptions ?

1. A

   Only one

   Only one. All four listed products come out of eruptions.

2. B

   Only two

   Only two. Under-counts.

3. C

   Only three

   Only three. Nitrogen compounds are also volcanic gases.

4. D

   All four

   All four. Pyroclasts, ash, nitrogen and sulphur compounds.

Summary. Official key is (d) all four. Eruptions throw pyroclastic debris, ash and dust, and gases that include sulphur compounds (SO2, H2S) and nitrogen compounds (N2, NOx traces). None of the four is alien to volcanism.