In Ruby, which of the following is NOT a valid loop construct?

A. case B. while C. for D. if

A. while B. until C. for D. do...while

A. Executes code if condition is true B. Executes code if condition is false C. Breaks out of loop if condition is true D. Executes code only once if condition is true

A. To define a class B. To handle multiple conditions with one expression C. To declare a variable D. To perform mathematical calculations