单项选择题 请从下列选项中选择关于元模型描述正确的选项（）

未知题型 Suppose you were Phil’s colleague, write a letter of condolence to his widow. 1. express your sorrow at hearing of Phil’s death 2. mention something you remember about the deceased or recall something you’ve heard others say

未知题型 酵母备压管道清洗原理备压管的清洗一般采用碱-热水清洗方法，碱液洗涤剂一般为2－3％的氢氧化钠溶液，溶液的浓度与洗涤效果尤为相关（）