3. As shown in Figure 1, Angel used 18 toothpicks to build a three-story staircase. Following this pattern, to build a five-story staircase, she would need ( ) more toothpicks.
(A) 9
(B) 18
(C) 20
(D) 22
(E) 24
3. D.

As shown in Figure 2, notice that it takes 4 toothpicks to build one step; it takes 10 toothpicks to build two steps, an increase of 6; it takes 18 toothpicks to build three steps, an increase of 8. Thus, the additional number of toothpicks forms an arithmetic sequence. Therefore, to build 5 steps, it will require an additional $10+12=22$ toothpicks.