Subscript in a pair of brackets
The compound sodium carbonate is a strong electrolyte because it completely dissociates when placed in water into its component ions. The equation of the reaction can be expressed as:

The dissociation leads to the formation of sodium and carbonate ions with the latter held together by its internal covalent bond.
This is unlike weak electrolytes that do not dissociate completely in water or aqueous solutions. Only a small fraction of the solute exists as ions in the solution.
More on strong and weak electrolytes can be found here: brainly.com/question/3410548
The correct answer is B. An observation
Explanation:
An observation is defined as a statement or conclusion you made after observing or measuring a phenomenon, this includes statements based on precise instruments. For example, if you conclude a plant grows 2 inches every month by measuring the plant during this time, this is classified as an observation. The conclusion of the student is also an observation because he concludes this after analyzing the volume of the water in the cylinder through the lines in the graduated cylinder, considering the water is just in the middle of 100 mL and 200 mL which indicates there are 150 mL of water.
Hello!
Work=Force*Displacment
Work=.05N * .07m = .0035J
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