No
No, then is not a preposition. It is a conjuction.Than is a preposition.
At is a preposition. Anything that can be ___ the box is a preposition. For Example: At the box.
If is not a preposition. It is a conjunction.
If a preposition does not have an object, it is not a preposition. It is an adjective, adverb, or possibly a conjunction.
A prepositional phrase begins with a preposition and ends with an object of a preposition.
The lackluster battle was punctuated by sporadic mortar fire.
to be sporadic and without pattern to be sporadic and without pattern
His aim was sporadic and the bullet holes were scattered randomly.
Shopping without a list may only fulfill sporadic needs. My sporadic shopping helps me to buy in bulk.
We huddled in our trenches, listening to sporadic enemy gunfire.
sporadically
Sporadic means not occurring every time - it's a once-in-a-while change.
sporadically
Nothing
He came in at 12:00am and said where are my students?
Whatever I say it is
sporadic!