A、When he saw a lot of people come to the exhibition. B、When he found one of his son’s paintings had been hung up by mistake. C、

Never a very confident man, Hanley was happy to leave all the arrangements for the exhibition to his agent, a young man by the name of Green, who had a talent for organization. Green had been to his studio and, with the help of Hanley’s wife, had selected the pictures for the exhibition. He had decorated the hall and had personally supervised the hanging of the pictures. Most important of all, he had seen to it that all the invitations went to the right people: critics, reporters and, of course, people with money to spend on paintings.
    "There’s no doubt about it," Green assured him during the exhibition," everything has gone off very well. "Hanley was pleased, but remained shyly in the background, unwilling to meet his public.
    "One picture caught special attention. "Green told him.  He consulted his catalogue.  "Number thirty-seven. It did not have a name, so your wife and I decided to call it’ Midnight’-- because all the colors are very dark."
    Hanley, unable to recognize the picture from this description, was puzzled, but he said nothing. When everyone had left, he slipped across to see for himself the painting which had attracted so much attention. He laughed so much that Green came across to see what the matter was. Trying hard to suppress his amusement, Hanley told him that one of his son’s paintings had been hung up by mistake.