动植物的生活离不开能量，在细胞中分解有机物，提供能量的结构是（     ）

A．叶绿体

B．线粒体

C．细胞膜

D．细胞核

The workers trapped in the coal mine never got ________ because they encouraged one another, and

after 9 days and nights they were all saved.[ ]

A. desperate  

B. ready  

C. cheerful  

D. surprised