一句英语应该只有一个谓语动词，怎么这句话会有3个呢？

If the difference between an antibody and an antigen is small,the affinity between an antibody and an antigen is higher,sore cognition is also more likely.

该说每一个单独的句子有一个谓语动词。你的句子包含了三个单独句子。

1. If the difference between an antibody and an antigen is small
2. the affinity between an antibody and an antigen is higher,
3. sore cognition is also more likely.
故三个谓语。

句子分为简单句和复杂句。没有任何连词或者只有一个谓语的句子叫做简单句，其余是复杂句。 这个句子是复杂句。标志是and 这个连词 ， 它可以把动词（就是谓语）并列连接起来。 谢谢采纳啦。 这3动词都是谓语。