A candlelit dinner works wonders for romance. Now scientists say it could also be good for your heart. Breathing in candle smoke causes beneficial【C1】______in your heart rhythm, they claim. It is thought that tiny salt particles released when the candle burns are【C2】______the effect The researchers monitored the hearts of 13 men and women as they breathed in air【C3】______into a small chamber. In some【C4】______the air included smoke from candles in a second room. The volunteers didn"t know which type of air they were breathing, but when it included candle smoke, their heart rate variability【C5】______. Everyone"s heart rate varies【C6】______all the time, beating a little bit faster when we breathe in than when we breathe out This is perfectly healthy and a sign that the brain is【C7】______and able to regulate the heart But this variation【C8】______as we get older and if we【C9】______heart problems. In the study, it was increased by【C10】______candle smoke. Researcher Christina Isaxon said the concentration of smoke【C11】______during the study was similar to that created by a candlelit dinner. As the volunteers could not see the candles and weren"t told what they were breathing, the effect could not be explained【C12】______by the calming effect of candlelight. Dr Isaxon believed that tiny particles of the candle smoke could be responsible for the beneficial effects. These particles are【C13】______regulating the heart"s rhythm and in sending messages between cells in the body. More salts are produced when a【C14】______is still. The study did not find any【C15】______health effects of the smoke—【C16】______she admitted she did not "make a huge effort" to find any. Soot, black powder in the smoke, from lit candles has been【C17】______health problems in the past. The American Chemical Society has warned that common wax candles release【C18】______harmful chemicals linked to cancer and other illnessea It recommends using beeswax. Dr Isaxon used candles made of a natural fat in her study. She recommended using candles that are as natural as possible and avoiding【C19】______and dyes as they may give off【C20】______chemicals when burned.
【答案解析】解析：基于was similar to的语义，可认为研究者比较了“研究中的烟雾浓度”(the con-centration of smoke．．．during the study)和“烛光晚餐所释放的烟雾浓度”(that created by acandlelit dinner)。C项generated“产生，生成”能对应that后的created一词，代入后指“研究中蜡烛燃烧产生的烟雾的浓度”。
单选题
【C12】
【正确答案】
B
【答案解析】解析：在该项研究中，志愿者看不到蜡烛，也未被告知所呼吸的气体，因此不能把“烛光具有镇静效果”(the calming effect of candlelight)看作是改善心率的原因。B项away置于ex-plained后，意为“为……辩解”，代入后与谓语中的could not be一起表达“不能把……当作理由”之意。其他三个选项不与explain搭配。
单选题
【C13】
【正确答案】
D
【答案解析】解析：既然蜡烛烟雾中含的微小颗粒对心脏有好处，那么它们对心率应该具有调节作用(regulating the heart"s rhythm)。D项involved in意为“参与；与……相关联”，代入后可指烟雾中的微小颗粒帮助调节心率,语义符合要求。