19. A, B, C, D, E stand in a row, satisfying that A is not adjacent to B and C, and D is not adjacent to E. The number of different arrangements is ( ) .
(A) 12
(B) 16
(C) 28
(D) 32
(E) 40
19. C.

There are two scenarios:
(1) If A is at one of the ends, there are two choices; the person next to A cannot be B or C, so there are two choices from D and E; D and E cannot be adjacent, so one person is chosen from B and C, which gives two choices; the last two positions are filled by the remaining two people. Therefore, there are
$$
2 \times 2 \times 2 \times 2=16
$$

different arrangements.
(2) If A is not at the ends, there are three choices; A cannot be adjacent to B or C, so A can only be placed in the two positions that are not adjacent to A, which gives two choices; the remaining two positions adjacent to A are filled by D and E, which gives two choices. Therefore, there are
$$
3 \times 2 \times 2=12
$$

different arrangements.
Thus, there are a total of $16+12=28$ different arrangements.
24. A.