Hi, can i get a distinction level answers for this question please? Part a,b & c. Thanks

a) What is this a description of? "A linear crystallographic defect or irregularity within a crystal structure that contains an abrupt change in the arrangement of atoms." b) When jet airliners were first used there were a number of instances of them breaking up in mid-air. A possible cause was thought to be their square windows. Q6 C3.2 Explain why this might have been the case and why all windows in aircraft are now round or rounded. c) In metals and alloys how can large grain sizes and contaminants reduce strength in metals and alloys