因为您正在比较（问题 === 答案）。这应该是（响应 === 答案）。

条件未使用正确的左赋值。

演示： https://jsfiddle.net/y4orwqqu/

 var quiz = [
    ['What is the capital of New York', 'Albany'],
    ['What is the Capital of California', 'Sacramento'],
    ['What is the capital of New Jersey', 'Trenton'],
    ['What is the capital of Virginia', 'Richmond']
];

var questionsRight = 0;
var questionsWrong = 0;
var questionsRightList = [];
var questionsWrongList = [];

/* Don't NEED to declare the following right away, but it's good practice to go ahead
and declare the variables you're going to use. Notice you don't need to assign any
default value to them */
var question;
var answer;
var response;
var html;

function print(message) {
  document.write(message);
}


    for( var i = 0; i < quiz.length; i++) {
        // Get the first item from array[i] and set it as question
        question = quiz[i][0];

          // Get the second item from array[i] and set it as answer
        answer = quiz[i][1];

        // Get input from the user and set it to the response variable
        response = prompt(question);

        if (response.toLowerCase() === answer.toLowerCase()) {
            //questionsRight is initially 0. If response === answer               questionsRight = 0+1
            questionsRight += 1;    
        }
        // else {
        //  //questionsWrong is initially 0. If response === answer questionsWrong = 0+1
        //  questionsWrong += 1;

        // }
    } 

    html = "You got " +  questionsRight + " question(s) right.";

    print(html);