What geographic features of the Middle Colonies suggest
that they were well placed for trade?

The Middle Colonies were more diverse than colonies in New England and the South. Most of the early settlers depended on the fur trade and on farming for economic survival. The most populous of the Middle colonies was Pennsylvania, other colonies were settled rather haphazardly over the course of the 17th century. Settlers usually organized themselves in small farms spread throughout the colony with a few cities added to the mix.

The Middle Colonies were not as cohesive as the New England colonies because colonists in this region were not united by single religion or code of beliefs.Area dominated by larger farms than N.E., smaller than the S.; still there is an emphasis on subsistence rather than cash crops. Settlement patterns generally revolve around single family farms (around 50 -150 acres).  Again you see the predominance of servant (as opposed to slave labor) in the 17th century.  [A notable exception is in New York where you see a large number of African Americans in the colony, especially in New York city where blacks are employed in commercial settings and as dockworkers.]The Middle Colonies were settled by different nationalities so there is greater emphasis on religious toleration and cultural diversity. This is especially true in the colony of New York.

I hope it helps.