What is a barrier to skill development?

How long is the garonne? Why is art museum in Copenhagen named Louisiana? Who named Rottnest Island and the Swan River? What was the latest disappearance in the Bermuda Trianngle? As you were walking over the London bridge you met a London school boy he tipped his hat and drew his cane and in this rhyme you said this boys name? Where is the Great Lakes Naval Memorial And Museum - Uss Silversides in Muskegon Michigan located? What were the significant events of Dr. Jose Rizal's tour in Germany? How far can you park from a firelane? How many rivers are there in the US? Where in Paris is the Eiffel Tower located? In what country will you find raindeer lake and raindeer river? Where is the Nuckolls County Museum in Superior Nebraska located? How is the earth's atmosphere unlike an ocean? Why do tropical hardwood trees have small spacing between their annular rings? How many buildings and rooms are the in Mission San Miguel Arcángel? How do you get over your fear of loops on roller coasters? Is the river shannon tidal? Which capital city has the largest museum? What is said to be the biggest weakness of steel for building ships? What was the the purpose of the San Juan Bautista bells?

What is a barrier to skill development?