The Boolean function with the Karnaugh map

First, observe that columns 01 and 11 are entirely filled with 1s. Since B is 1 in both columns, the term B covers these cells. Next, look at the remaining 1s where B is 0 (columns 00 and 10). In column 00, the single 1 is at row 11 (CD=11), representing CD. In column 10, the 1s are at rows 01 and 11 (CD=01 and CD=11), representing D. Combining these gives the expression (A + C)D + B.