Assume that interest rates on $20-$year Treasury and corporate bonds are as follows:

T$-$bond $=7\mathrm{.}72\%$ AAA $=8\mathrm{.}72\%$ A $=9\mathrm{.}64\%$ BBB $=10\mathrm{.}18\%$

The differences in these rates were probably caused primarily by:

Question $26$ options:

Tax effects.

Default and liquidity risk differences.

Maturity risk differences.

Inflation differences.

Real risk$-$free rate differences.