Which conjunction best connects the subjects in the sentence?

either a clown a juggler will entertain the children at the party.

but

or

and

Population parameters are difficult to calculate due to

This was a 1676 uprising in the virginia colony

Dunkin' donuts is expanding in several different countries. its stores offer curry doughnuts in india, dulce de leche doughnuts in peru, and cherry brandy doughnuts in germany. this is an example of segmentation based primarily on: