There was this same question posted on chegg but I think it was wrong? I'm not sure. Please take a look! I am not sure if it's D or B

An investor is considering a BB-rated bond but is concerned with the possibility that the market premium for this bond may widen against the Treasury yield curve. Which of the following most closely matches the risk the investor is referring to

A. yield curve risk

B. downgrade risk

C. maturity risk

D. credit spread risk