Questions

The meanings of the given words are as follows:
Nefarious: (typically of an action or activity) wicked or criminal
Sloppy: careless and unsystematic; excessively casual
Flurry: a small swirling mass of something, especially snow or leaves, moved by sudden gusts of wind

Unassertive: (of a person) not having or showing a confident and forceful personality

Ignoble: not honourable in character or purpose
Modest: unassuming in the estimation of one's abilities or achievements
Subtle: (especially of a change or distinction) so delicate or precise as to be difficult to analyse or describe
Gregarious: (of a person) fond of company; sociable
Magnanimous: generous or forgiving, especially towards a rival or less powerful person
Iniquitous: grossly unfair and morally wrong
Atrocious: horrifyingly wicked
Therefore, it can be observed that option E i.e.

‘iniquitous, atrocious’ forms a synonym- synonym pair of ‘nefarious’.

Decomposing waste in the landfills, by the action of microorganisms, produce methane and carbon dioxide. Landfill gas consists of 40-60% of methane and rest is carbon dioxide. Trace amount of volatile organic compounds (<1) are also present which mainly comprise of hydrocarbons.