Read the given passage carefully and answer the following questions.

A study by Scripps Institute of Oceanography has revealed that Ocean Noise has increased tenfold since the 1960s. Oceanologists Sean Wiggins, John Hildebrand from Scripps and Mark McDonald from Whale Acoustics, Colorado studied the declassified US Navy documents and came to the conclusion that global shipping has contributed a lot to increase undersea noise pollution. They said with populations increasing around the globe in recent decades, the underwater world has also become a noisier place, adding that the effects of greater noise on marine life was still unknown. Findings revealed a tenfold increase in underwater ocean noise as compared with the 1960s. They said the noise levels in 2003-2004 were about 10-12 decibels higher than in 1964-1966. The reasons could be due to the vast increase in the global shipping trade, the number of ships plying the oceans and the higher speed of vessels.

If the average ocean noise level is 40 decibels in 2003-2004, it was about, ______ decibels in 1964-66.

29

The correct answer is Option (3) → 29

The passage states that the noise levels in 2003–2004 were about 10–12 decibels higher than in 1964–1966.

• If the average noise level in 2003–2004 was 40 decibels,

• Then in 1964–1966, it would have been:
  40 – (10 to 12) = 28 to 30 decibels

The only option within that range is 29 decibels.