阅读下面短文并回答问题，然后将答案写到答题卡相应的位置上（请注意问题后的词数要求）。
[1]People with lower intelligence are more likely to be unhappy than their brighter colleagues, according to UK researchers, Their study of 6,870 people showed low intelligence was often linked with lower income and poor mental health, which contributed to unhappiness. The researchers are calling for more help and support to be targeted at people with lower IQs. Their findings were published in the journal Psychological Medicine.
[2]The researchers analyzed data from the Adult Psychiatric Morbity Survey in England. One of the questions was：“Taking all things together, how would you say you were these days—very happy ,fairly happy or not too happy?” The highest part saying they were “        ”was found in people with an IQ between 120 and 129-43% said they were very happy..
[3]However, the highest proportion saying “not too happy”was found in people with an IQ between 70 and 79. The study said lower intelligence was linked to lower income, worse health and needing help with daily life, such as shopping or housework—all of which contributed to unhappiness.
[4]Dr Hassiotis said：“There is some evidence that long term strategies directed at young children from poor backgrounds can have a positive impact on IQ, wellbeing and life opportunities”. Such interventions(干涉)are likely to be costly, but the initial costs may be offset（抵消）by future benefits such as a reduced reliance on state benefits and better mental and physical health”.
[5]He added that the study was particularly helpful as it identified some of the factors（因素）that influence the association between IQ and happiness. The study also emphasized the interventions to prevent lower IQ leading to greater unhappiness.
小题1:What does the passage mainly talk about?(no more than 10 words)
                                                                                            
小题2:Fill in the blank in paragraph2 with proper words.(no more than3 words)
                                                                                           
小题3:Costly as the interventions(干涉)are , why is it worthwhile to do so ?.(no more than 10 words)
                                                                                           
小题4:What did Hassiotis want to stress in the last paragraph?(no more than 6 words)
                                                                                           
小题5:What does the word “which” referred to in paragraph one ?(no more than 6 words)