To meet Euro-II emission standards, what should be the sulphur content in the ultra low sulphur diesel?

The correct answer is A) 0.05 percent or less than this. Euro-II norms set a maximum sulphur content of 500 ppm (0.05%) in diesel. The wording "or less than this" matters because the norm is a ceiling, not an exact value.

Why the other options fail:

• B) 0.15% and C) 0.10% are not the benchmark limits of any Euro or Bharat Stage norm.
• D) 0.20% (2000 ppm) is the older Euro-I-era limit, which is much looser than Euro-II.

The core concept is the progressive tightening of vehicular emission norms. Sulphur content in fuel affects catalytic converters and particulate emissions, so lower sulphur is a precondition for later norms. Euro-III (350 ppm) and Euro-IV (50 ppm) followed. For Mains, this links to the urban air pollution and fuel-quality policy in GS-3 (Environment).

Note that India has since moved to BS-VI, which requires 10 ppm sulphur from April 2020. The 50 ppm "ultra low sulphur" diesel of the BS-IV period is a different benchmark from the Euro-II figure asked here.

Trap: Candidates confuse the 50 ppm ULSD (BS-IV) figure with Euro-II, or pick 0.20% because it is the Euro-I limit. Remember that Euro-II is 500 ppm, which is 0.05%.