About half of all babies are able to walk independently by months of age.

I think that about half of all babies are able to walk independently by 12 month of age. It said that babies tend to take their first steps from the age of 9. Babies usually start to crawl before they can walk. This is because their arm are usually more effective. After crawling they learn to stand up with their feet first and later learn to walk while holding things. The next step after that is walking. 
Not all babies walk at the same time. There those that learn before the other so there is no need to worry if your child does not walk by 12 months.

Its either a) or b),wind and water erosion gradually widen the canyon