first Questions, how to get hard curves in a smooth surface and etc

 From:  nukkle
first,, moi3d seems to be a quite noce piece of software, i am maing my tryouts to
take a final decision if i buy it.

hi this are my first attempts with te moi3d trial

as u can see on the picture there is a nurbs surface
made out of 3 curves. i ve attached the file.

My questions:
A. the surface is very smoth and round, or curvy,,,frmo curve to curve. how can i make the surface get a hard line in it, where the yellow curves are

B.How can i make a surface bewteen B and C . B is one part of a whole curve that i cant, select, how to?

kind regards