This is my visual force page :

<apex:page standardController="Transaction__c" extensions="myControllerExtension">

<apex:form >
<h1>New Transaction</h1>
<apex:pageBlock >

<apex:pageBlockButtons location="top">
<apex:outputLabel value="Select Transaction Type:"/>
<apex:selectList multiselect="false" size="1" value="{!selectedValue}">
<apex:selectOptions value="{!options}"/>
<apex:actionSupport event="onchange" reRender="pbSection" status="pStatus"/>
</apex:selectList>
<apex:actionStatus id="pStatus" startText="Rendering..."/>
</apex:pageBlockButtons><br/><br/>

<apex:pageBlockSection id="pbSection" >
<apex:pageBlockSectionItem rendered="{!selectedValue='Credit'}">
<apex:outputLabel value="Credit:"/>
<apex:inputField value="{! Transaction__c.Credit__c}"/>
</apex:pageBlockSectionItem>
<apex:pageBlockSectionItem rendered="{!selectedValue='Debit'}">
<apex:outputLabel value="Debit:"/>
<apex:inputField value="{! Transaction__c.debit__c}"/>
</apex:pageBlockSectionItem>
</apex:pageBlockSection>
<br/><br/>

<apex:pageBlockSection >
<apex:inputField value="{! Transaction__c.To_Account_Number__c}"/><br/>
</apex:pageBlockSection>
<apex:pageBlockSection >
<apex:inputField value="{! Transaction__c.Transaction_Amount__c}"/><br/>
</apex:pageBlockSection>
<apex:pageBlockSection >
<apex:inputField value="{! Transaction__c.Transaction_Date__c}"/><br/>
</apex:pageBlockSection>

<apex:pageBlockSection >
<apex:commandButton action="{! save}" value="Save!"/>
</apex:pageBlockSection>
</apex:pageBlock>
</apex:form>

</apex:page>

And this the apex class :

public with sharing class myControllerExtension {

    private final Transaction__c trans;
    
    // The extension constructor initializes the private member
    // variable acct by using the getRecord method from the standard
    // controller.
    public myControllerExtension(ApexPages.StandardController stdController) {
        this.trans= (Transaction__c)stdController.getRecord();
    }

    public String selectedValue { get; set; }

    public List<SelectOption> getOptions() {
        List<SelectOption> options = new List<SelectOption>();
       
        options.add(new SelectOption('Credit','Credit'));
        options.add(new SelectOption('Debit','Debit'));
        return options;
    }
    
    public myControllerExtension () {
        selectedValue = 'Credit';
    }


   
}

My problem is that when i am running this page , I cannot see "Credit" & "Debit" input field.

In my apex class i had defined constructor , initializing its value to "Credit" but input field is not seen not even after changing it to debit.

Please help.