How can DNA be precipitated from a mixture of biomolecules?

The correct answer is Option (1) → By treating with chilled ethanol

To cut DNA with restriction enzymes, it must first be made pure. The cells are broken open with enzymes (lysozyme for bacteria, cellulase for plant cells, chitinase for fungi). RNA is then removed with ribonuclease and proteins with protease. Finally, chilled ethanol is added, and the purified DNA comes out of the solution (precipitates). It can be seen as a collection of fine threads in the suspension and is removed by spooling.

NCERT Extract:
Isolation of the Genetic Material (DNA) – “… RNA can be removed by treatment with ribonuclease whereas proteins can be removed by treatment with protease. Other molecules can be removed by appropriate treatments and purified DNA ultimately precipitates out after the addition of chilled ethanol. This can be seen as collection of fine threads in the suspension (Figure 9.5).”