Final answer:
The spindle forms in a haploid cell during Mitosis.
Step-by-step explanation:
The correct answer is c) Mitosis. During mitosis, a spindle forms in a haploid cell. In mitosis, the sister chromatids within the cell separate, forming two new daughter cells with the same number of chromosomes. This is similar to what happens in meiosis II, where the sister chromatids within the two daughter cells also separate, forming four new haploid gametes. However, in meiosis I and interphase, a spindle does not form in a haploid cell.