A developer has a Visualforce page and custom controller to save Account records. The developer wants to display any validation rule violation to the user. How can the developer make sure that validation rule violations are displayed?

A developer needs to create a custom visualforce button for the opportunity object page layout that will cause a web service to be called and redirect the user to a new page when clicked. Which three attributes need to be defined in the <apx:page> tag of the visualforce page to enable this functionality?

A developer executes the following query in Apex to retrieve a list of contacts for each account:
List<account> accounts = [Select ID, Name, (Select ID, Name from Contacts) from Account] ; Which two exceptions may occur when it executes? (Choose two.)

A reviewer is required to enter a reason in the comments field only when a candidate is recommended to be hired. Which action can a developer take to enforce this requirement?

How can a developer warn users of SOQL governor limit violations in a trigger?