Of course, men, children, bears and birds are vastly more interested in the
delicious berries than in the fertilization process. As in the case of most berry-
bearing species, the raspberry depends upon the birds to drop ________
undigested seeds over the country so the new colonies may arise under freer
conditions. Indeed, one of the best places for the budding ornithologist to take
opera-glasses and note-book is to a raspberry patch early in the morning.

Which choice completes the text so that it conforms to the conventions of
Standard English?
A) their
B) they're
C) its
D) it's
​