As shown in the figure, given ab ∥ CD, guess what is the relationship between ∠ B, ∠ bed, ∠ D in Figure 1, figure 2 and figure 3? Please show their relationship by equation and prove one of them. (1)______ ；（2）______ ；（3）______ ．

As shown in the figure, given ab ∥ CD, guess what is the relationship between ∠ B, ∠ bed, ∠ D in Figure 1, figure 2 and figure 3? Please show their relationship by equation and prove one of them. (1)______ ；（2）______ ；（3）______ ．

(1) Take Figure 1 as an example, it is proved that a straight line EF parallel AB, ∫ ab ∥ CD, ∥ EF ∥ CD, ∫ B = ∠ bef (two straight lines parallel, equal internal stagger angle), ∫ d = ∠ def (two straight lines parallel, equal internal stagger angle); ∫ bef + ∥ def = ∠ bed, ∫ B + ∥ d = ∠ bed