Answer: D. Prices would decline and interest rates would rise.
Step-by-step explanation:
Increase in Supply: When the supply of a financial instrument, such as short-term securities, increases, other things being equal, prices tend to fall because there are more securities available for purchase, which can put downward pressure on prices.
Effect on Interest Rates: As prices of existing securities fall, their yields (interest rates) tend to rise. This is because as prices go down, the fixed interest payments on these securities become a higher percentage of the lower price, resulting in a higher yield.
So, an increase in the supply of short-term securities is likely to lead to a decrease in their prices and an increase in interest rates. Option D correctly describes this scenario.