Which of the following additional care is required to enable children to use the scale properly and learn?
I. To introduce children to the marking of sub-units on the scale.
II. Properly placing the scale with the measuring object.
III. Estimating length before finding the actual length.
IV. Calculate length correctly.
1. II, III and IV
2. Only IV
3. I, II, III and IV
4. I, II and IV