When looking at the options given:
- Option B, "The letter T indicating thymine," indicates a strand of DNA. Thymine is one of the four nitrogenous bases found in DNA, along with adenine, guanine, and cytosine. These bases pair up specifically in DNA; adenine pairs with thymine, and guanine pairs with cytosine. Therefore, the presence of the letter T (indicating thymine) is a clear indication of a DNA strand.
- Option A is not a clear indicator of a DNA strand. It could represent various things in different contexts and does not directly point to DNA.
In summary, the letter T indicating thymine is the option that indicates a strand of DNA, as thymine is a crucial component of DNA's structure.
