正则表达式：为什么匹配的是ab而不是a啊

Question

var s = 'Hi, do you (know) your abcs?';const regex1 = /ab?/gi;console.log(regex1.exec(s));

Answer 1

var s = 'Hi, do you (know) your abcs?';

const regex1 = /ab??/gi;

console.log(regex1.exec(s));