This morning, Barb must not only finish a research paper due this afternoon, but also prepare a presentation for her evening class tonight. Today's stress should telomerase activity, thereby potentially the telomeres.

- Decrease; lengthening.

Explanation:

As per the question, Barb's today's stress must decrease the telomerase activity as he would feel more chronic strain thinking about the completion of these stressful tasks like 'finishing the research paper and preparing the presentation for tonight'. This might have led to the lower levels of telomerase, thereby possibly 'lengthening the telomeres'. Such states of chronic stress require increased telomerase activity to deal with the complications of these stress and avoid the imprudent destruction of DNA.

i dont know sorry why dont you looking it up on google