Mike is A genius.By the time he graduated,He Had been offered jobs by a dozen computer companies. 这个句子里有错误吗？

这个句子没有明显的语法错误，但是有一个拼写错误。应该将"A"改为"a"，因为"genius"是一个可数名词，需要使用不定冠词"a"来修饰。另外，如果想要表达“一打”公司，可以将"a dozen"改为"dozens"。因此，完整的句子应该是： Mike is a genius. By the time he graduated, he had been offered jobs by dozens of computer companies.