阅读下列短文，从每题所给的四个选项(A、B、C和D)中，选出最佳选项。

Leon McCarthy, 12, was born without fingers on his left hand. That didnˈt stop him from being able to do many tasks. But Leon could not grasp more than one object at a time. So Leonˈs father, Paul, created a Prosthesis(假肢), using a 3D printer. Now Leon has fingers that open and close. “It was a do－it－yourself, father－and－son adventure，” says Paul.

When Leon was a baby, his doctor advised his parents not to give him a prosthetic hand until he was in his early teens. “The doctor said Leon should first learn to get full use out of the hand he was born with，” says Paul. As Leon got older, his father looked into buying a prosthetic hand, which can cost as much as $30，000. Paul found a more affordable solution.

One day, Paul discovered a video on the Internet about Robohand, a prosthesis created with a 3D printer. He downloaded the free instructions and called Robohandˈs creators for advice. They told him all he needed was a 3D printer—which costs around $2，000—and some materials.

Luckily, Leonˈs school had recently purchased a 3D printer and it offered to help Paul build the hand for Leon. “We used a soccer shinguard(护胫), cardboard, and tape. They cost about $10，” says paul.

With his new hand, Leon can do things better. “I can help my mom more, because now I can carry two grocery bags，” he says.

Leonˈs father has already built several hands for Leon. Leon helps design each one. He says thereˈs one thing in particular that he wants to do with a future prosthesis. “The goal，” he says, “is to be able to tie my shoelaces(鞋带)．”