题目内容：
根据下列短文，回答题。The secret to happiness is keeping busy, research has found. Keeping the mind 36 with tasks-no matter how meaningless-staves off(赶走) negative emotions, the study found.
However, the bad news is that humans seem hard-wired (天生的) to be lazy in order to save energy, according to Professor Christopher Hsee, a behavioral scientist at Chicago University.
In a study 98 students were asked to complete two surveys. After they had completed the first they were made to wait 15 minutes to receive the next one. They were given a choice of either handing in the first 37 nearby or at a more distant location they had to walk to. Whichever option they chose, they received a chocolate bar. Two- thirds (68 per cent) chose the lazy 38 . Those who had taken the walk reported feeling happier than those who bad stayed 39
Prof Hsee 40 keeping busy helped keep people happy. He said the findings, reported in the journal Psychological Science, had policy 41 "Governments may increase the happiness of idle citizens by having them build bridges that are 42 useless," he proposed. At the individual Ievel, he advised, "Get up and do something. Anything. Even if there really is no point to what you are doing, you will feel better for it. " He 43 , "Incidentally, thinking deeply or engaging in self-reflection 44 as keeping busy, too. You do not need to be running around--you just need to be 45 , either physically or mentally. "
A． study
B． added
C． thought
D． option
E． engaged
F． especially
G． increased
H． implications
I． survey
J． solutions
K． occupied
L． concluded
M． counts
N． put
O． actually
第36空答案为（ ）。
参考答案：
答案解析：