Depends on the question. .
for example: ' what is heart attack? give its causes?'
now for this question they have allotted 2.5 marks for what is heart attack and 2.5 marks for its causes. Ab app khud socho. . 2.5 marks k liye kitna likhoge? half page ya chalo one page will be enough. . and give 5 to 6 causes. 1 page front and back will be enough. .