Exams

Secondary pollutants include ozone, which is formed when hydrocarbons (HC) and nitrogen oxides (NOx) combine in the presence of sunlight.

Whereas Primary pollutant are those pollutants that are directly emitted from their sources, like CO2, CO, SO2 as these gases are directly emitted form burning of fossil fuels.

Acid rain, which is formed when sulfur dioxide or nitrogen oxides react with water, sulfuric acid etc.

Hence, Acidrain is a secondary air pollutant.

Viswanathan Anand continued his excellent run bagging a bronze in the World Blitz Chess Championship following his gold winning performance in the Rapid section.

• The World Blitz Chess Championship is a chess tournament held to determine the world champion in chess played under blitz time controls. Since 2012, FIDE has held an annual joint rapid and blitz chess tournament and billed it as the World Rapid & Blitz Chess Championships.

• The current world blitz champion is Magnus Carlsen.

In chemistry, the term transition metal has three possible meanings: The IUPAC definition defines a transition metal as "an element whose atom has a partially filled d sub-shell, or which can give rise to cations with an incomplete d sub-shell".

Any of the set of metallic elements occupying a central block (Groups IVB–VIII, IB, and IIB, or 4–12) in the periodic table, e.g. iron, manganese, chromium, and copper. Chemically they show variable valency and a strong tendency to form coordination compounds, and many of their compounds are coloured.

Here in the given options, only iron (Fe) is a transition metal since Strontium is an alkaline earth, arsenic is a metalloid, hydrogen is (normally) a diatomic gas.

Dull means not sharp, not shining, not bright, ...

Hence, the given words are all that means the opposite of dull.