Linear motion is one directional motion which requires only one dimension to explain it. This motion is along a straight line.
In all other options either the motion is taking place along a curved path(as in option D) , thereby making it a curvilinear motion or the motion is taking place at some angle (as in option A and B) thereby making it angular motion.
Well…I do not agree with the scientist’s claim because when a protein is denatured all of its structures are destroyed except the peptide bonds in primary structure. The secondary, tertiary and all other structure get completely useless and cannot be annealed to recover their function and activity.