What is formed as glaciers retreat and leave debris behind in mounds at the front of their farthest advance?

I believe it is terminal moraines. I hope I answered your question, my friend. :)

Why you put last one a? i think is b.

The us is first  the  u.s. economy  remains the  largest in the world  in terms of nominal  gdp. however, the  u.s. economy  loses its spot as the number one  economy  to china when  measured  in terms of  gdp  based on ppp. in these terms, china's  gdp  is $23.19 trillion exceeds the  u.s. gdp  of $19.42 trillion