Final answer:
The expected percent change in the content of a eukaryotic cell, in terms of DNA, as it goes through the S phase of the cell cycle, is a plus 100 percent increase, which means the cell doubles its DNA.
Step-by-step explanation:
You're asking about the expected percent change in the content of a eukaryotic cell as it progresses through the cell cycle from the start of the phase to the end of the phase. During the cell cycle, eukaryotic cells undergo various phases including interphase (which comprises the First Gap (G1), Synthesis (S), and Second Gap (G2)) and the mitotic phase (M). During the S phase of interphase, the cell replicates its DNA, which means that by the end of this phase, the cell will have twice the amount of DNA it started with.
Therefore, the expected percent change in the content of a eukaryotic cell, in terms of DNA, by the time it completes the S phase, is a plus 100 percent increase. So, if we're specifically talking about DNA content, the correct answer to your question would be d) Plus 100 percent.