Based on your provided text, here’s how you can fill in the blanks:
Item A is a triple beam balance and is used to measure the mass of an item.
Item B is a spring scale and is used to measure the weight of an item.
So the completed sentences would be:
Item A is a triple beam balance and is used to measure the mass of an item.
Item B is a spring scale and is used to measure the weight of an item.