Which one of the following items is not normally an important requisite for agriculture?

Fertilizers typically provide in varying proportion, the three major plant nutrients. Which of the following is not among the major plant nutrients provided by fertilizers?

Among the following acid food item pairs. Which pair is incorrectly matched?

Which one of the following ore-metal pairs is not correctly matched?

Which type of lenses are prescribed for the correction of astigmatism of human eye?

Some substances, such as carbon dioxide change from a solid to a gas when heated, without becoming liquid in between. This is known as