架子鼓是一种打击乐器，雏形起源于中国，最早可追溯到明朝时期。如图所示，当用大小不同的力敲击时，发出声音的       （选填“音调”、“响度”或“音色”）不同。

Have you ever wondered ______ there are so many natural disasters across the world in 2010?

A．which it is that

B．what is it that

C．how it is that

D．why it is that