To solve this problem, we need to identify which of the given options does not contain DNA. Let's analyze each option:$\newline \bullet$Chloroplast:$\newline$ - Chloroplasts are organelles found in plant cells and some algae.$\newline$ - They contain their own DNA, which is separate from the nuclear DNA.$\newline$ - This DNA is involved in coding for some of the proteins required for photosynthesis.$\newline$ - Therefore, DNA is present in chloroplasts.$\newline \bullet$Ribosomes:$\newline$ - Ribosomes are cellular structures responsible for protein synthesis.$\newline$ - They are composed of ribosomal RNA (rRNA) and proteins.$\newline$ - Ribosomes do not contain DNA.$\newline$ - Therefore, DNA is not present in ribosomes.$\newline \bullet$Nucleus:$\newline$ - The nucleus is the control center of a eukaryotic cell.$\newline$ - It contains the cell's genetic material in the form of DNA.$\newline$ - Therefore, DNA is present in the nucleus.$\newline \bullet$Mitochondria:$\newline$ - Mitochondria are known as the powerhouses of the cell.$\newline$ - They contain their own DNA, which is separate from the nuclear DNA.$\newline$ - This DNA is involved in coding for some of the proteins required for mitochondrial function.$\newline$ - Therefore, DNA is present in mitochondria.$\newline$Based on the analysis, the correct option is Option 2: Ribosomes, as they do not contain DNA.