In the context ofwhich one of the following are the terms 'pyrolysis and plasma gasification' mentioned?

1. A

   Extraction of rare earth elements

   (a) Extraction of rare earth elements. REE processing uses other chemical routes; pyrolysis and plasma gasification are not the usual REE tags, so this is not the key.

2. B

   Natural gas extraction technologies

   (b) Natural gas extraction. Those terms are not fracking or CBM vocabulary, so this is not the key.

3. C

   Hydrogen fuel-based automobiles

   (c) Hydrogen fuel-based automobiles. Hydrogen cars are a different file; pyrolysis/plasma gasification are waste-treatment terms, so this is not the key.

4. D

   Waste-to-energy technologies

   (d) Waste-to-energy technologies. Pyrolysis thermally decomposes waste without full combustion; plasma gasification uses a plasma torch to syngas-ify residues. Both appear in municipal and hazardous waste-to-energy literature. That context is the official key.

Summary. Official key is (d) waste-to-energy technologies. Pyrolysis and plasma gasification convert solid waste to oil, char or syngas rather than only dumping or simple incineration. They are not rare-earth, natural-gas or hydrogen-car processes. Honour the stored letter (d).