title: With the use of Apex code, how can I select all ''OpportunityProducts' objects which are belongs to particular 'Opportunity Id'
body: <p>I am way to customizing 'Sales' application that belongs to 'salesforce.com' platform. 
  Is there any way to select all the 'OpportunityProducts' objects which are belongs to particular 'Opportunity Id' ? </p>
  
  <pre><code>[SELECT Id FROM  OpportunityProduct WHERE Opportunity =:opportunitId];
  </code></pre>
  
  <p>When I execute above code for select those 'OpportunityProduct', I got following error. If any one have some idea please update me. Thanks. </p>
  
  <pre><code>Save error: sObject type 'OpportunityProduct' is not supported. If you are attempting to use a custom object, be sure to append the '__c' after the entity name. Please reference your WSDL or the describe call for the appropriate names.
  </code></pre>