I’m not sure sorry I really wish I could help
Answer:
Electric field, 
Explanation:
It is given that,
Mass of sphere, m = 2.1 g = 0.0021 kg
Charge, 
We need to find the magnitude of electric field that balances the weight of a plastic spheres. So,

a = g



or

Hence, the magnitude of electric field that balances its weight is
. Hence, this is the required solution.
Answer:
it is double the temperature change of iron
What does "which" mean ? Does it mean to pick the right one out of a list that you're hiding from us ?
There's no way we can begin to make a choice if we don't know WHAT the samples are samples OF.
I CAN give you some info, however, that will probably help you make the right choice from the hidden list that you have.
If water is on the list, then that's the answer, EXCEPT if liquid ammonia is on the list. Liquid ammonia is the only known substance on Earth that beats water as the answer to this question.
If neither liquid ammonia NOR water is on your secret list of samples, then you're on your own, Bunky.