Happiness and sadness are states of being states of being that define the way we view the world. It is often said that some people by nature have a sunny character. Now scientists may have discovered why. Some people may be hard-wired for happiness, while others are genetically negative, as scientists have suggested in a study published in late February, in a British journal Proceedings of the Royal Society B. Earlier research had already established that the gene known as 5-HTTLPR plays a key role in determining how the neurotransmitter (神经传递素) serotonin (血清素) works within the brain. Serotonin, a hormone (荷尔蒙), passes chemical messages between nerve cells. It has been closely linked to mood. Several anti-depressant (抗抑郁) drugs regulate serotonin levels. Scientists had also identified three variants of the gene. Two so-called "short" variants were linked to a higher risk of depression and suicide attempts. Unlike the two "short" variants, the "long" variant of 5-HTTLPR showed a clear dislike of negative images, such as fierce animals, and a clear liking for positive ones, such as flowers. Researchers from the University of Es in Britain, led by Elaine Fox, showed participants a series of images. The images were divided into three kinds: negative ones aimed at inspiring fear or stress such as a spider or person about to commit suicide, pleasant ones and neutral ones. “The participants who had the long variant of the 5-HTTLPR gene showed a clear dislike of negative material alongside a careful attention for positive material,” the researchers found. They paid close attention to the pretty pictures, and ignored the frightening ones. On the other hand, the short variant groups had the opposite reaction. In January, the Australian government organized "happiness workshops", teaching government staff how to be happy. The department that held the "happiness workshops" said unhappy staff weren't productive staff. Australian political opposition parties have argued that the "happiness workshops" are probably a waste of money and couldn't increase productivity as intended. However, whether the workshop will have a happy or disappointing result, we will have to wait and see. 67．Form the third paragraph, we know that . A．affected by 5-HTTLPR, the neurotransmitter serotonin works within the blood B．there are 5 variants of 5-HTTLPR genes which control people’s moods C．how the neurotransmitter serotonin works is greatly determined by 5-HTTLPR D．5-HTTLPR receives chemical messages from verve cells 68．What does “It” in the sentence “It has been closely linked to mood.” in the 3rd paragraph refer to? A．Serotonin. B．A nerve cell. C．5-HTTLPR. D．The brain. 69．If a person had the long variant of 5-HTTLPR, he or she would probably . A．like the images of spiders B．prefer the images of crocodiles C．enjoy an image of green tress D．suffer from depression very often 70．What can we infer from the passage? A．People’s moods can change a little bit under the influence of certain drugs. B．Researchers showed participants of the research two kinds of images. C．A person possesses one long and one short variant of 5-HTTLPR at the same time. D．The author firmly believes that “happiness workshops” will not change people’s moods.