As she walked round the huge department st

问题：

As she walked round the huge department store, Edith reflected how difficult it was to choose a suitable Christmas present for her father. She wish that he was as easy to please as her mother, who was always delighted with perfume.
Besides, shopping at this time of the year was a most disagreeable experience; people trod on your toes, poked you with their elbows and almost knocked you over in their haste to get to a bargain ahead of you.
Partly to have a rest, Edith paused in front of a counter where some attractive ties were on display. "They are real silk", the assistant assured her, trying to tempt her. "Worth double the price. " But Edith knew from past experience that her choice of ties hardly ever pleased her father.
She moved on reluctantly and then quite by chance, stopped where a small crowd of man had gathered round a counter. She found some good quality pipes on sale—and the prices were very reasonable. Edith did not hesitate for long: although her father only smoked a pipe occasionally, she knew that this was a present which was bund to please him.
When she got home, with her small well chosen present concealed in her handbag, her parents were already at the supper table. Her mother was in an especially cheerful mood, "Your father has at last to decide to stop smoking. " She informed her daughter.

Edith’s father smoked a pipe ______.

A．when he was obliged
B．on social occasions
C．from time to time
D．when he was delighted