Final answer:
The correct event that occurs during mitosis in a plant cell is the condensation of chromosomes during prophase. Cell wall formation, the attachment of sister chromatids at the centromere, and the duplication of chloroplasts are events of the cell cycle phases outside mitosis.
Step-by-step explanation:
During mitosis in a plant cell, the correct event that happens is A. Condensation of chromosomes, which occurs by supercoiling during the prophase of mitosis. This is when the loosely packed chromatin coils and condenses into visible chromosomes, each identifiable with its identical partner forming an X-shape known as sister chromatids. Option B, Cell wall formation, occurs during cytokinesis, which is not strictly part of mitosis, but is, in fact, the final step of the cell cycle where the cytoplasmic components are physically separated into two daughter cells.
In plant cells, this involves the formation of a cell plate that develops into separate cell walls. Option C, Sister chromatids attaching to each other at the centromere, while maintained into prophase, actually occurs during interphase in the DNA replication process during the S phase. Option D, Chloroplasts duplicate, also takes place during interphase, and not mitosis.