下列叙述中，与决定蛋白质多样性无关的因素是（）
A.肽键的数目
B.氨基酸的种类和排列顺序
C.核糖体的种类和数目
D.蛋白质的空间结构
参考答案：C
根据汉语提示完成下列句子，每空一词。
1. Study hard and (进步) every day.
2. Mr. Green has many friends at and . (国内外)
3. We are good friends, we have (保持联系)
each other for many years.
4. Remember not to rubbish . (到处乱丢)
Andy often helps her mother _____ the housework on Sunday. [ ]
A. to
B. with
C. for
D. of
