Add punctuation: Stitch and trim the seam allowances
A: Stitch and trim the seam allowances.

Add punctuation: The war is a crime in defiance of UNs decisions and thereby in defiance of the Danish constitution
A: The war is a crime in defiance of UN's decisions and thereby in defiance of the Danish constitution.

Add punctuation: The name Mesothelioma is derived from mesothelium which is the membrane that covers and protects most of the internal organs of the body
A:
The name Mesothelioma is derived from mesothelium, which is the membrane that covers and protects most of the internal organs of the body.