例句與造句

1. It is even unknown if the Whitehead group of " F " ( see Whitehead torsion ) or the projective class group of " F " ( see Wall's finiteness obstruction ) is trivial, though it easily shown that " F " satisfies the Strong Bass Conjecture.
2. It's difficult to find projective class group in a sentence. 用projective class group造句挺難的