Search:

Sure, go with "at". If you search on Google for people's assignment papers you'll get more results with "At the beginning" in any case.

This is a good reference I just found for more info, last...

"At the beginning" is a starting point for something, so it would be "At the beginning of the 21st century".

"At the beginning" is commonly used with years and points in time.

You're looking at...