目前被公认的细胞膜分子结构称什么？
参考答案：
被公认的细胞膜分子结构称流动镶嵌模型。
The old couple, ________ in the small village for years, can tell the names of all the villagers.
A．living
B．lived
C．having lived
D．to have lived
什么叫预先分级？根据什么来确定？
