问题：
[单选] One thing he felt regret for was that he never had the________of heating him play the piano．
One thing he felt regret for was that he never had the________of heating him play the piano．
问题：
[单选] As the teacher has announced，________will be open thmorrow．
As the teacher has announced，________will be open thmorrow．
问题：
[单选] 同一骨骼肌细胞在接受其运动神经元的冲动刺激后产生的2次终板电位中，第2个终板电位的振幅发生了变化，幅度明显降低，这可能是因为（ ）
同一骨骼肌细胞在接受其运动神经元的冲动刺激后产生的2次终板电位中，第2个终板电位的振幅发生了变化，幅度明显降低，这可能是因为（ ）
问题：
[单选] 全胃肠营养液中必需氨基酸和非必需氨基酸的含量是（ ）
全胃肠营养液中必需氨基酸和非必需氨基酸的含量是（ ）
