How should a developer verify that a specific Account record is being tested in a test class for a Visualforce controller?

A developer needs to create a Lightning page for entering Order Information. An error message should be displayed if the zip code entered as part of the Order's shipping address is not numeric.
What is a recommended way for the error message be displayed to the end user?

Part of a custom Lightning Component displays the total number of Opportunities in the org, which is in the millions. The Lightning Component uses an Apex Controller to get the data it needs. What is the optimal way for a developer to get the total number of Opportunities for the Lightning Component?

What is a benefit of JavaScript remoting over Visualforce Remote Objects?

Line 1 public class AttributeTypes Line 2 { Line 3 private final String[] arrayItems; Line 4 Line 5
@AuraEnabled Line 6 public List<String> getStringArray() { Line 7 String*+ arrayItems = new String*+,'red', 'green', 'blue' -; Line 8 return arrayItems; Line 9 } Line 10 } Consider the Apex controller above that is called from a Lightning Aura Component. What is wrong with it?