Which temperature do they need to perform the experiment for perovskite to conduct electric current? A: T=1980°C

B: T>1980°

C: T>_ 1980°C

D:T< 1980°C

For C it's suppose to be an less than equal sign .

What do electromagnetic waves carry? how are they produced through which media can they move? where do they transfer energy? what do they not transfer? what do mechanical waves carry? how are they produced? through which media can they move? where do they transfer energy? what do they not transfer?