If the expectations theory of the term structure of interest rates is correct, and if the other term structure theories are invalid, and we observe a downward sloping yield curve, which of the following is a true statement? and why?

Investors expect short-term rates to be constant over time. Investors expect short-term rates to increase in the future. Investors expect short-term rates to decrease in the future. It is impossible to say unless we know whether investors require a positive or negative maturity risk premium The maturity risk premium must be positive