Questions

Main memory - only large storage media that the CPU can access directly.

Secondary storage - extension of main memory that provides large nonvolatile storage capacity.

An operating system is a program that acts as an intermediary between the user and the computer hardware. The purpose of an OS is to provide a convenient environment in which user can execute programs in a convenient and efficient manner. It is a resource allocator responsible for allocating system resources and a control program which controls the operation of the computer hardware.

Photosynthesis is the process that converts solar energy into chemical energy. During the stage of light-dependent reactions involving photosystems I and II in photosynthesis, O2 produced.

It is due to the deficiency of Vitamin A. Retinol which is present in vitamin A. Its deficiency causes night blindness. It is available in carrots. 

Supply curves tend to be more elastic in the long run, because there is time for firms to enter or leave the industry.

Tetrad is a homologous chromosome pair in the given options. A homologous chromosome pair is a pair of chromosomes one from father and one from mother that has same gene sequence after the process of meiosis.

A sponge has many holes but it absorbs water and can hold them in it.