"Some alluvial deposits are a rich source..." can be read as "There are some alluvial deposits, each of which is a rich source..."How can the first part (plural) work
swell with the later part (singular)?
I don't know if there's a rule as such. Perhaps someone else will elaborate.What's the grammar rule here?
The word "a/an" has several meanings and functions. In this case it meansSome alluvial deposits are a rich source of diamonds.
See my signature...What's the grammar rule here?