The correct answer is option 2: Sulphuric acid. The atmosphere of Planet Venus is composed of thick and yellowish clouds that consist mainly of sulphuric acid. These clouds are formed by chemical reactions involving sulphur dioxide and water vapor in the atmosphere. The high temperatures and pressures on Venus cause the sulphur dioxide to react with other substances, resulting in the formation of sulphuric acid.

Option 1: Chlorine is not a major component of Venus` atmosphere. Although trace amounts of chlorine have been detected on Venus, it does not play a significant role in the composition of its atmosphere.

Option 3: Nitric acid is also not a major component of Venus` atmosphere. While there are small amounts of nitrogen compounds present, such as nitrogen dioxide, the dominant component is sulphuric acid.

Option 4: Bromine is not present in significant amounts in Venus` atmosphere. Bromine is a halogen that is not commonly found on Venus or other rocky planets.

Therefore, the correct answer remains option 2: Sulphuric acid.