The weights of 4 boxes are 20, 40, 80 and 90 kilograms. Which of the following cannot be the total weight, in kilograms, of any combination of these boxes and in a combination a box can be used only once?
A box is termed as eraser, an eraser is termed as pen, a pen is termed as stick, and a stick is termed as plant. Then in the exam a student will write with ___.