单项选择题

Psychologists discovered that people become "motivated" when they know an experience is about to be completed.
The University of Michigan study found that this (31) to a person thinking the experience would end (32) . The findings, reported in the journal Psychological Science, could add (33) to the saying "leaving the best for last".
"Endings (34) us in lots of ways and one is this ’positivity effect’," said researcher Ed O’Brien, (35) led the study."It is something (36) . You think ’I might as well (37) the benefits of this experience even though it is going to end’ or ’I want to get something good out of this (38) I still can’". He added, "When you (39) tell people something is the last, they may like that thing more."
In their study, they (40) male and female students five small chocolates of different flavors before asking them to (41) their enjoyment as they ate. The flavors were ranked (42) different orders with some volunteers being told the chocolate was their last while others received no such (43) .
The study found those with the warnings found the (44) chocolate tastier than others. Asked which chocolate was their favorite, those which knew chose it on more than two in three (45) . In contrast, those who were unaware rated it top in only 22 percent of cases.
Mr. O’Brien, a graduate student in social psychology, said that due to the chocolates being rated (46) , rather than all together at the end of the experiment, (47) the results could not be explained by difference in (48) . He added, "Many experiences have happy endings—from the movies and shows we watch to dessert at the end of the meal—and so many people may have a general (49) that things end well, which could (50) over into these unrelated or insignificant judgments.\