The correct answer is: Only conclusion II follows.
The statement “The use of non-conventional sources of energy will eliminate the energy crisis in the world” does not imply that modern technology is gradually replacing the conventional sources of energy. It is possible that non-conventional sources of energy will be used in addition to, or instead of, conventional sources of energy.
The statement does imply that the excessive exploitation of environment has led to depletion of conventional sources of energy. This is because non-conventional sources of energy are often seen as a way to reduce our reliance on fossil fuels, which are non-renewable and contribute to climate change.
Therefore, only conclusion II follows.