If the DNA content of a cell in G${}_1$ phase is 4C, what would be its DNA content in G${}_2$ phase?

The correct option is D 8C
DNA replication occurs during the S phase of interphase due to which the content of DNA gets doubled in the cell.
Interphase has a long duration and is divided into $G_1$, S and $G_2$ phases.
During $G_1$ phase, cells are metabolically active and cellular contents are synthesized and thus there is overall cell growth. $G_1$ phase is followed by S phase. DNA replication occurs in the S phase where DNA synthesis occurs and the content of DNA gets doubled. At the end of $G_1$ phase, each chromosome has one chromatid. But after the S phase, each chromosome will have two chromatids. These two chromatids are identical copies of each other. After S phase, the cell enters into $G_2$ phase and the DNA content remains the same as in S phase. Hence, if the DNA content in $G_1$ phase is 4C, then the DNA content in $G_2$ phase will be 8C. C here refers to the content of DNA.