if the angles of a triangle are in the ratio 2:3:4, then the difference between the greatest and the smallest angle is ____.

• A.  \[\text{10 }\!\!{}^\circ\!\!\text{ }\]                            
• B.  \[\text{20 }\!\!{}^\circ\!\!\text{ }\]    
• C.         \[\text{30 }\!\!{}^\circ\!\!\text{ }\]                
• D.         \[\text{40 }\!\!{}^\circ\!\!\text{ }\]