Final answer:
When book C is assigned first and D second, there are 2! permutations for the remaining two books, giving us 2 ways to assign the remaining books A and B.
Step-by-step explanation:
The subject question pertains to permutations and combinations, which is part of Mathematics. Given that the teacher needs to assign books A, B, C, and D, with C always assigned first and D second, we need to calculate how many arrangements of books A and B are possible in the remaining two positions.
Since the first two positions are fixed (C and D), there are two positions left to fill. There are 2 books to choose from for the third position and 1 book for the final position. Hence, the number of permutations is calculated as 2! (two factorial), which equals 2 x 1 = 2 ways.
The answer to the question of how many ways the teacher can assign the books if book C is chosen first and D is chosen second is thus B) 2 ways.