膜蛋白
参考答案：
生物膜所含的蛋白叫膜蛋白，是生物膜功能的主要承担者。
I had invited 50 guests to the party, but actually twice _____ came. [ ]
A. more than
B. as many
C. as much
D. less than
如何为儿童客人服务？（7分）
