落魄音乐家甲将自己唯一的一架钢琴卖给了乙，但与乙约定，甲先暂时借用此钢琴进行创作。后甲创作到情绪极度暴躁状态，一气之下将钢琴抛弃。钢琴被丙拾得，丙将钢琴卖给了不知情的丁。此时，钢琴的所有权人是( )

A．甲

B．乙

C．丙

D．丁

Table tennis is easy to learn, and, by the same token, boys don't need a lot of space to practice it.

A．by the same rule

B．symbolically

C．moreover

D．by logic