Answer: right; left
Step-by-step explanation:
When the Treasury bond market becomes less liquid, other things equal, the demand curve for corporate bonds shifts to the right and the demand curve for Treasury bonds shifts to the left.
Liquidity is highly sought after in the bond market such that more liquid securities have a higher demand than less liquid securities.
Should Treasury bills become less liquid, their demand would decrease which would result in the demand curve for treasury bills shifting to the left.
More people would then switch over to Corporate bonds which would have more liquidity. The increase in demand for corporate bonds will lead to the demand curve for corporate bonds shifting to the right.