【单选题】

Once upon a time a poor farmer taking a sack of wheat to the mill did not know (1) to do when it slipped from his horse and fell (2) the roaD、The sack was (3) heavy for him to (4) , and his only hope was that (5) some one would come riding by and (6) a hanD、

It was not long (7) a rider appeared, but the farmer’s heart sank when he (8) him, for it was the great man who lived in a castle nearby. The farmer (9) have dared to ask (10) farmer to help, or any poor man who might have come (11) the road, but he could not beg a (12) of so great a man.
(13) , as soon as the great man came up he got (14) his horse, saying, "I see you’ve had bad luck, frienD、How good it is (15) I’m here just at the (16) time. " Then he took one (17) of the sack, the farmer the other, and between them they lifted it on the horse.
"Sir," asked the farmer, "how can I pay you "
"Easily enough," the great man (18) . "Whenever you see (19) else in trouble, (20) the same for him. \
A．knew
B．understood
C．remembered
D．recognized