Comprehensive Research on the Main Influences of the Shape of the Treasury

Comprehensive research on the main influences of the shape of the Treasury yield curve was done by Antti Ilmanen in a series of papers. He finds that there are three main influences. Which of the below is NOT one of these main influences?

A) One influence concerns the market's expectations of future rate can changes (in a way predicted by the pure expectations theory) .
B) One influence concerns bond risk premiums.
C) One influence concerns convexity bias.
D) One influence concerns convexity premiums (in a way predicted by the preferred habitat theory) .