Hi Anamar,
This would depend on the question type you're using. If you're using multiple choice, fill in the blank, multiple answer, or another question type where you can specify a correct answer, then the system would be able to automatically grade it as zero points for any question that students failed to select or enter an answer. However, if you're using something like essay questions, where the answer is freeform, you will have to manually grade it through speedgrader, like shown in this guide.
