General Science Questions

A pure solid and a pure liquid are definitely a single phase because they are so united, or homogeneous. This leads to a homogeneous mixture also being a single phase.

Hence, the option that cannot be considered a single phase is A. a heterogeneous mixture.

DNA stands for Deoxyribo nucleic acid. It is a nucleic acid made up of monomeric unit called Nucleotide.

A nucleotide consist of -

a) Sugar - Deoxyribose in DNA ( ribose in RNA)

b) An organic base- Adenine, cytosine, guanine.

A living community and its environment is what an ecosystem is.

Dairy products like milk, cheese and yogurt are rich source of protein as well as calcium also. 

The gas usually filled in the electric bulb is Nitrogen.

A Book always has Pages. Without pages it can't be called as a book. A book can be either with or without preface, text or index but it can't be without a page.

Hence, A Book always has page.