The answer is the fourth one (D): mitosis, condense.
Explanation for each option:
A. Meiosis, condense - This is incorrect. Meiosis is a type of cell division that reduces the chromosome number by half and is involved in the production of gametes. The process of separating identical chromosomes after replication is not meiosis, and chromosomes condense during mitosis, not meiosis.
B. Mitosis, separate - This is partially correct. Mitosis is indeed the process that separates identical chromosomes after replication. However, the process begins when the chromosomes condense, not when they separate.
C. Meiosis, fuse end to end - This is incorrect. Meiosis does not involve chromosomes fusing end to end. Instead, it involves the separation of homologous chromosomes and then sister chromatids.
D. Mitosis, condense - This is correct. Mitosis is the process that separates the new identical chromosomes after replication, and it begins when the chromosomes condense. During prophase of mitosis, the chromatin condenses into visible chromosomes, which is the initial step in the process of mitosis.
In summary, the correct answer is D: mitosis, condense.