To solve this problem, we need to determine which substance can be used to precipitate DNA out of a mixture of biomolecules. Let's analyze each option:$\newline \bullet$Option 1: Isopropanol$\newline$ - Isopropanol can be used to precipitate DNA, but it is not as effective as ethanol when it comes to chilling.$\newline \bullet$Option 2: Chilled ethanol$\newline$ - Chilled ethanol is commonly used for DNA precipitation. It helps in the aggregation of DNA molecules, making them visible as a precipitate.$\newline$ - Ethanol is effective because it reduces the solubility of DNA in the solution, especially when chilled.$\newline \bullet$Option 3: Methanol at room temperature$\newline$ - Methanol is not typically used for DNA precipitation, especially at room temperature, as it is less effective than ethanol.$\newline \bullet$Option 4: Chilled chloroform$\newline$ - Chloroform is used in DNA extraction to remove proteins and other contaminants, but it is not used for DNA precipitation.$\newline$Based on the analysis, chilled ethanol is the most suitable option for precipitating DNA.$\newline$Therefore, the correct option is Option 2: Chilled ethanol.