The reaction of a soil refers to its acidity or alkalinity. It is acidity or alkalinity. It is an important indicator of soil health. It can be easily measured and is usually expressed by the pH value. 
i. Most soils are in the pH range of 5 – 8, while the range for plant growth is within pH 3 – 10.
ii. Unfavourable high pH values, as observed in alkali soils, can be decreased by amendment with materials such as gypsum, elemental S or iron pyrites. 
iii. pH of 7.5 – 8.5 is generally called the neutral range.
iv. Plants are generally more sensitive to strong alkalinity, where the dominant cation is often Na, than to strong acidity where the dominant cation is H. Out of the following which combination of statements are correct?