Input: Read this: A number of medications are being studied for multi drug resistant tuberculosis including: bedaquiline and delamanid. Bedaquiline received U.S. Food and Drug Administration (FDA) approval in late 2012. The safety and effectiveness of these new agents are still uncertain, because they are based on the results of a relatively small studies. However, existing data suggest that patients taking bedaquiline in addition to standard TB therapy are five times more likely to die than those without the new drug, which has resulted in medical journal articles raising health policy questions about why the FDA approved the drug and whether financial ties to the company making bedaquiline influenced physicians' support for its use 
Question: When did delamind receive FDA approval?

Output: unanswerable


Input: Read this: In 1867, Prince Alfred, Duke of Edinburgh and second son of Queen Victoria, visited the islands. The main settlement, Edinburgh of the Seven Seas, was named in honour of his visit. Lewis Carroll's youngest brother, the Reverend Edwin Heron Dodgson, served as an Anglican missionary and schoolteacher in Tristan da Cunha in the 1880s.
Question: When did Tristan da Cunha visit the islands?

Output: unanswerable


Input: Read this: Navigation is based on a variety of senses. Many birds have been shown to use a sun compass. Using the sun for direction involves the need for making compensation based on the time. Navigation has also been shown to be based on a combination of other abilities including the ability to detect magnetic fields (magnetoception), use visual landmarks as well as olfactory cues.
Question: What is navigation based on?

Output: a variety of senses


Input: Read this: Mass production of glass window panes in the early twentieth century caused a similar effect. In glass factories, molten glass was poured onto a large cooling table and allowed to spread. The resulting glass is thicker at the location of the pour, located at the center of the large sheet. These sheets were cut into smaller window panes with nonuniform thickness, typically with the location of the pour centered in one of the panes (known as "bull's-eyes") for decorative effect. Modern glass intended for windows is produced as float glass and is very uniform in thickness.
Question: How was the bull's-eye used?

Output:
for decorative effect