please rewrite this without using parentElement.classList.add or document.querySelector

function loadQuestion$($questionIndex$)\{$

var currentFieldset $=$ document.getElementById$(\text{'}$question$-\text{'}+$ questionIndex$)$;

if $(!$currentFieldset$)\{$

window.alert$(\text{'}$Invalid question index.$\text{'})$;

return;

$\}$

$//$ Hide all fieldsets

var allFieldsets $=$ document.getElementsByTagName$(\text{'}$fieldset$\text{'})$;

for $($var i $=0$; i $<$ allFieldsets.length; i$++)\{$

allFieldsets$[$i$].$style.display $=$ 'none';

$\}$

$//$ Show the next question

var nextFieldset $=$ document.getElementById$(\text{'}$question$-\text{'}+$ questionIndex$)$;

if $($nextFieldset$)\{$

nextFieldset.style.display $=$ 'block';

$\}$

$//$ Update progress bar

var progressPercentage $=($questionIndex $/$ totalQuestions$)*100$;

progressBar.style.width $=$ progressPercentage $+\text{'}\%\text{'}$;

$//$ Hide the "Next Question" button until "Check Answer" is clicked

nextQuestionButton.style.display $=$ 'none';

$\}$

function checkAnswer$($questionIndex$)\{$

var selectedAnswer $=$ null;

var radioButtons $=$ document.getElementsByName$(\text{'}$answer$-\text{'}+$ questionIndex$)$;

for $($var i $=0$; i $<$ radioButtons.length; i$++)\{$

if $($radioButtons$[$i$].$checked$)\{$

selectedAnswer $=$ radioButtons$[$i$]$;

break;

$\}$

$\}$

if $(!$selectedAnswer$)\{$

window.alert$(\text{'}$Please select an answer.$\text{'})$;

return;

$\}$

var correctAnswer $=$ document.getElementById$(\text{'}$correct$-$answer$-\text{'}+$ questionIndex$).$value;

if $($selectedAnswer$.$value $===$ correctAnswer$)\{$

selectedAnswer.parentElement.classList.add$(\text{'}$highlight$-$correct'$)$;

correctAnswerCount$++$; $//$ Increment correct answers count

$\}$ else $\{$

selectedAnswer.parentElement.classList.add$(\text{'}$highlight$-$incorrect'$)$;

var correctAnswerInput $=$ document.querySelector$(\text{'}$input$[$value$="\text{'}+$ correctAnswer $+\text{'}"]\text{'})$;

if $($correctAnswerInput$)\{$

correctAnswerInput.parentElement.classList.add$(\text{'}$highlight$-$correct'$)$;

$\}$

$\}$

$//$ Show the "Next Question" button

nextQuestionButton.style.display $=$ 'block';

if $($questionIndex $===$ totalQuestions$)\{$

displayCompletionMessage$($correctAnswerCount$)$; $//$ Use the correctAnswerCount variable directly

$\}$

$\}$