In order to calculate the thermal energy, first let's calculate the power, using the formula:

For a voltage V = 9 Volts and a resistance R = 50 ohms, we have:

Now, multiplying the power by the time (in seconds), we can find the energy:

In scientific notation, we have an energy of 7.3 * 10^2 J, therefore the correct option is the fourth one.
The Nucleus contains Protons and Neutrons.
The Neutrons does not have a charge.
The Protons are positively charge.
Hence the charge on the Nucleus, would be the charge of the proton, which is positive.
Hence Nucleus is Positively Charged.
When you add more water to the balloon, it makes it heavier. Therefore it would weigh the balloon down ( increasing mass) and increasing the energy to plummet down. So the answer is B.
Yes you can, with using scientific experiment.
Ask a question -- Do background Research -- Construct a Hypothesis --Test with an Experiment -- Procedure working? -- Yes or no? -- Analyze Data and Draw Conclusions
With an experiment you can discover if its correct or not.
Hope this helps ! <3