You will be given a definition of a task first, then some input of the task.
In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.

Question: What country is the National Institute of Health located in? Passage:While working at the National Institute of Health, Lisziewicz worked to find a gene therapy approach to treat HIV/AIDS. She based her research on discovering if small portions of gene-stopping DNA (called antisense oligonucleotides) could be created to bind up the viral RNA in retroviruses like HIV so that the virus could not make more copies of itself to continue the infection. Small pieces of messenger RNA (or mRNA) carry a copy of the cell's DNA to the ribosomes where the mRNA directs the ribosomes to create the proteins that the cells need. Viruses (like HIV) have their own set of mRNA, and they use the ribosomes of the cell they infected to make new viruses to propagate the infection throughout the body. Lisziewicz's idea was to create antisense oligonucleotides that are complementary to the HIV's viral mRNA. These complementary DNA pieces can bind to the HIV viral mRNA and prevent the HIV virus from replicating itself. The use of antisense oligonucleotides worked very well in cell cultures, and was quickly transferred to clinical trials.
Links: a. National Institutes of Health b. HIV/AIDS c. National Institutes of Health d. Gene therapy
Output:
a