Which of the following would tend to lower the equilibrium interest rate on a…

Which of the following would tend to
lower
the equilibrium interest rate on a bond issued by the ABC Corporation?
a)
a decrease in the liquidity of ABC’s bonds trading in the secondary market.
b)
an improvement in ABC’s bond rating from A to AA.
c)
an increase in the economy’s inflation rate.
d)
new information that ABC corporation is planning to file for bankruptcy protection.