Anywhere between 1 and 4 marks... Its highly unlikely that ppsc would award more than 4 marks... There is a difference between wrong question (e.g - rough endoplasmic reticulum one) and confusing statement (e.g speed of sound which is 1246 at room temperature) ... Also, there is a difference between wrong options of a question (e.g instrument to measure rainfall) , and options that are confusing or not agreed upon by all (e.g layers of atmosphere)... Therefore, i think that the claim of 20 wrong questions would be reduced to 3 or 4 questions and compensation would be given accordingly... Re exam is also unlikely since 3 or 4 wrong questions don't warrant doing the whole exercise again, and that it could affect the reputation of the commission along with setting a wrong precedent... Let's be realistic and build expectations in line with ground realities...