https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1122139/
C. 6.81x10^-4
It is negative 4 because the 6 is 4 digits away from the first 0.
Scientific notation has one number and then the decimal place so it can not be A or E.
In general, the most materially advanced and developed countries are focused on extensive development of the secondary sector of their economy. Because secondary sector is made up of Construction and Manufacturing, which the advanced and developed countries would like to focus on.
I can help if you tell us the the question! :)
Donald Trump building a wall.