Is steel a mixture or pure substance?

Question 3(multiple choice worth 4 points) (02.04 lc) which best describes the function of chloroplast? allows certa molecules to enter and exit the cell makes food during photosynthesis detoxifies waste products o packages proteins into vesicles

Number and variety of living organisms includes genetic, species, and ecological types

I’m stuck on this question cuz i’m stupid sksksksk