_____more than one hundred elements are known,only twenty—five of them are common and important.

A. Because
B. Although
C. If
D. Whether


出自:国家开放大学理工英语三

完成拼图验证

按住下方滑块,将拼图拖到缺口处后松开。

拼图背景,将小拼图拖到缺口处
向右拖动滑块