Hello,

when you answer a question you should ensure that you give the exact points and present it in a presentable manner by listing out important points, marking imprtant lines, including diagrams and markings, etc.

When an invigilator corrects your answer he/she may have some idea of what they expect to see in the paper and when your answer lacks that point then they reduce your marks.

Full marks will only be given to the most perfect answer. So next time when you loose marks make sure that you discuss with your faculty to understand where you can improve. It may also happen that they may have made some mistake while grading so check for such mistakes and notify them of the same.

Good Luck