Questions

Milk is not a pure substance since it has so many constituents that can be separated physically.

Compounds are pure substances formed from elements unlike mixtures.

A Hole gets bigger and bigger as you take more away from it.

Envelope is a letter holder for one letter and in the question it mean that it holds one letter. Eye is also a word which starts and end with E but has one letter in the middle.

Add the following function prototype in main ():

float f ( int, float );

Maglev trains are used in Japan, South Korea and China only.

Maglev derived from magnetic levitation using the principle of magnetic repulsion is a system of train transportation that uses two sets of magnets, one set to repel and push the train up off the track as in levitation then another set to move the 'floating train' ahead at great speed taking advantage of no friction. Maglev trains are therefore quieter and smoother than conventional trains, and have the potential for much higher speeds

Despite over a century of research and development, maglev transport systems are in operation in just three countries Japan, South Korea and China.

Hence Maglev -- Magnetic-levitation.

A magnifying glass is a convex lens that is used to produce a magnified image of an object. It is also called a hand lens in laboratory contexts.