what were the major reasons for post world war 2 Suburban growth? which of these were the most important?

Question

The Comtemporary city Urban studies

Answer 1

I think you mean in the USA which was not bombed.
10 to 12 million young men returning from the war and starting families - that was the main reason. Home building became industrialized / standardized with pre-planned residential communities like Levittown, PA - that was the second reason.

Excerpt below from Wiki is a good summary :

Levittown, Pennsylvania, is a suburban community, planned and built by Levitt & Sons. The majority of the land on which it is built was purchased in 1951. Houses built in Levittown consisted of just six models, including the Levittowner, the Rancher, the Jubilee, the Pennsylvanian, the Colonial and the Country Clubber. Levitt & Sons constructed only single-family dwellings in the community, each surrounded by a lawn, with only modest exterior variations, modern in style, with built-in appliances and landscaping. The homes were moderately priced and required only a low down payment. Construction of Levittown began in February 1952, soon after completion of Levittown, New York, located on Long Island. Levittown, Pennsylvania, was the second "Levittown" built by William J. Levitt, who is often credited as the creator of the modern American suburb. What set Levittown apart from other developments at the time was that it was built as a complete community.

Answer 2

off the top of my head:

replacing bombed out towns;
increased birth rate (initially prompted by the return of soldiers, and the welfare state, as well as the lesseneed threat of war.)

probably the former was most important, because housing simply had to be replaced.

Answer 3

what country?

in the US there was increased building of roads and highways leading up to, and after WWII. it allowed people to live outside of cities and commute for work. plus the baby boom after the war helped increase the population and the demand for housing.