20 litres of a mixture contains milk and water in the ratio 5 : 3. If 4 litres of this mixture are replaced by 4 litres of milk, the ratio of milk to water in the new mixture will become:
Significant beneficial effect of smoking occur primarily in the area of mental health, and the habit originates in a search for contentment. The life expectancy of our people has increased greatly in recent years; it is possible that the relaxation and contentment and enjoyment produced by smoking has lengthened many lives. Smoking is beneficial.
Which of the following, it true, weaken the above conclusion ?