Suppose that the firms in the perfectly competitive oat industry are currently receiving a price of $2 per bushel for their product and there are constant returns to scale. The minimum possible average total cost of producing oats in the long run is $1 per bushel. Other things being equal, it follows that:

The firms make a $1 per bushel in profit.

Explanation:

When the price is greater than the long run total costs, then a profit is being generated.  This helps the firms in the perfectly competitive oat industry to remain in the industry since they are making 100% profit on their investments, which they may not get elsewhere.  If they are not making such large profits, some of the firms may decided to leave the industry and relocate their resources to other industries where they can make enough profits.

e would be the answer