Stephen is reading a book for his history class. He is going to read 23 pages each day. If the book is 276 pages long, which equation could be used to determine the number of days, d, that it will take Stephen to read the entire book?

a. 23d = 276
b. d - 23 = 276
c. 23 + d = 276
d. d ÷ 23 = 276