题目

Reducing the amount of salt in our diets could save nearly 20,000 lives in the UK every year, according to researchers. The recommended maximum daily intake for adults is 6g in the UK, although just month the World Health Organization (WHO) revised this down to 5g. Yet according to figures from the British Heat Foundation, men consume around 9.7g a day, while women have 7.7 g. Fast foodSalt Content Original chicken2.9g per portion (份) Spicy crayfish3.5g per portion Large chips1 per portion McDonald’s Big Mac2.1 per portion Not researchers at three universities, including Harvard Med17．选择氧气、氢气、二氧化碳、一氧化碳的化学式填空：（1）有毒的气体是CO；（2）能用于灭火的气体是CO2；（3）对环境保护最理想的燃料是H2；（4）只能用排水法收集的气体是CO．