________, the boys were shouting and singing. [    ]

A. Happy and excited  

B. Happily and excited

C. Happily and excitedly  

D. Happy and excitedly

电冰箱里的食物容易“变干”和相互“窜味”，从物理学角度分析，食物“变干”主要是通过______方式失去水分的，食物“窜味”属于______现象．将水果用保鲜膜包好后再放入冰箱的冷藏室内，这是为了______．