`Delta\ A B C\ a n d\ Delta\ A B D` are on a common base `A B ,\ a n d\ A C\ =\ B D\ a n d\ B C\ =\ A D` as shown in Fig. 18. Which of the following statements is true? `DeltaA B C~=DeltaA B D` `DeltaA B C~=DeltaA D B` `DeltaA B C~=DeltaB A D`