How can I put points on multiple-choice questions but the one who answered will not know?

Yes, you can assign points for single-choice or multiple-choice questions without the users knowing.
To do this, access the Open settings of the single-choice or multiple-choice element and enable the "Calculation value" option inside this Open Settings. Then, assign the calculation value for each option. To view the total points, add a Form Calculation field to your form and input the calculation formula in this field. Ensure that you hide this Form Calculation field so that users cannot see it.