Short Corp

Short Corp.just issued bonds that will mature in 10 years,and Long Corp.issued bonds that will mature in 20 years.Both bonds promise to pay a semiannual coupon,they are not callable or convertible,and they are equally liquid.Further,assume that the yield curve is based only on expectations about future inflation,i.e.,that the maturity risk premium is zero for government bonds.Under these conditions,which of the following statements is correct?

A) If the yield curve is upward sloping and Short has less default risk than Long, then Short's bonds must have the lower yield under all conditions.
B) If the yield curve is downward sloping, Long's bonds must have the lower yield under all conditions.
C) If the yield curve is flat, Short's bond must have the same yield as Long's bonds under all conditions.
D) If Long's and Short's bonds have the same default risk, their yields must be equal under all conditions.