What are the characteristics for mechanical waves

Five students had to answer the question how are elements arranged in a periodic tabledamon: i think the elements are arranged by increasing massflo: i think the elements are arranged according to their properties sienna: i think the elements are arranged by when their discovers kyle: i think the elements are arranged according to how common they areglenda: i don't agree with any of themwho is right

7. what temperature is need to just dissolve 50 g of nh4cl in 75 g of water? '

What layer of the atmosphere is directly above the troposphere?