Giúp mình giải đề này với

What precautions should you take to prevent injuries when dealing with heavy loads?

Thermal stresses are developed in a metal when its a) initial temperature is changed b) final temperature is changed c) density is changed d) thermal deformation is prevented e) expansion is prevented f) contraction is prevented

The higher the astm grain-size number, the coarser the grain is. a)-true b)-false