请讲解一下这道题目，并给出图解---**Question Stem:** 4. 如图, 直线a∥b, 矩形ABCD的顶点A在直线b上, 若∠2=41°, 则∠1的度数为 ( ) **Translation of Question Stem:** 4. As shown in the figure, line a∥b, vertex A of rectangle ABCD is on line b. If ∠2=41°, then the measure of ∠1 is ( ) **Options:** A. 41° B. 51° C. 49° D. 59° **Chart/Diagram Description:** * **Type:** Geometric figure illustrating parallel lines and a rectangle. * **Main Elements:** * **Lines:** Two horizontal parallel lines labeled 'a' and 'b', with line 'a' above line 'b'. * **Rectangle:** A quadrilateral labeled ABCD, with vertices A, B, C, D. Vertex A is on line b. Vertices B and C are above line a. Vertex D is below line a. * **Points:** A, B, C, D are vertices of the rectangle. * **Angles:** * ∠1 is formed by the line segment AB and the line b, located at vertex A, inside the rectangle. * ∠2 is formed by the line segment AB and the line a, located near vertex B, outside the rectangle. * **Labels:** Lines are labeled 'a' and 'b'. Vertices are labeled A, B, C, D. Angles are labeled '1' and '2'. **Given Information:** * Line a is parallel to line b (a∥b). * ABCD is a rectangle. * Vertex A is on line b. * ∠2 = 41°. **To Find:** * The measure of ∠1.