Probably many of you know the idiom "an eye for an eye and a tooth for a tooth". But do you believe a tooth for an eye? That's something a little bit different. This strange exchange is neither a form ofretribution  nor an unexpected gift from the Tooth Fairy --- it's actually a very generous gift from a young Irishman, Robert McNichol, 23, to his formerly blind father, 57-year-old Bob McNichol. In 2005, Bob McNichol's sight was destroyed in an accident when his eyes weredoused(......)with liquidaluminum . Doctors predicted that he would never be able to see again. But McNichol never liked to take no for an answer: when he heard about a unique operation called Osteo-Odonto-Keratoprosthesis, he knew he had to _ , even though the success rate was a mere 65 percent. In the technique, the eyesocket  is rebuilt and implanted  with a human tooth and part of the jawbone, to provide support for an artificialcornea . Luckily for McNichol, Robert was willing to sacrifice one of his teeth to help his father regain his sight. The technique isn't simple: McNichol's first stint on the operating table lasted ten hours, with a five hour follow-up session at a later date. But thanks to his son's gift, he's already seeing astonishing results. "Now I have enough sight for me to get around and I can watch television. I have come out from complete darkness." he told his friends. The tooth Bobert donated to his father is used to   _   .
make the eye socket look prettier cause his jawbone to function well help his father take in more food support the implanted artificial cornea
Question: Probably many of you know the idiom "an eye for an eye and a tooth for a tooth". But do you believe a tooth for an eye? That's something a little bit different. This strange exchange is neither a form ofretribution  nor an unexpected gift from the Tooth Fairy --- it's actually a very generous gift from a young Irishman, Robert McNichol, 23, to his formerly blind father, 57-year-old Bob McNichol. In 2005, Bob McNichol's sight was destroyed in an accident when his eyes weredoused(......)with liquidaluminum . Doctors predicted that he would never be able to see again. But McNichol never liked to take no for an answer: when he heard about a unique operation called Osteo-Odonto-Keratoprosthesis, he knew he had to _ , even though the success rate was a mere 65 percent. In the technique, the eyesocket  is rebuilt and implanted  with a human tooth and part of the jawbone, to provide support for an artificialcornea . Luckily for McNichol, Robert was willing to sacrifice one of his teeth to help his father regain his sight. The technique isn't simple: McNichol's first stint on the operating table lasted ten hours, with a five hour follow-up session at a later date. But thanks to his son's gift, he's already seeing astonishing results. "Now I have enough sight for me to get around and I can watch television. I have come out from complete darkness." he told his friends. The tooth Bobert donated to his father is used to   _   .
A. make the eye socket look prettier
B. cause his jawbone to function well
C. help his father take in more food
D. support the implanted artificial cornea
Answer: