To solve this problem, we need to understand the role of the Anaphase Promoting Complex (APC) in mitosis and the consequences of its malfunction.$\newline \bullet$The Anaphase Promoting Complex (APC) is a crucial protein complex that regulates the progression of cells from metaphase to anaphase during mitosis.$\newline \bullet$APC functions by tagging specific proteins for degradation, particularly securin, which inhibits separase.$\newline \bullet$When securin is degraded, separase is activated, allowing it to cleave cohesin, the protein complex that holds sister chromatids together.$\newline \bullet$This cleavage is essential for the separation of sister chromatids, enabling their segregation to opposite poles of the cell.$\newline$If APC is defective, the following consequences are expected:$\newline \bullet$Securin will not be degraded, leading to the continued inhibition of separase.$\newline \bullet$As a result, cohesin will not be cleaved, and sister chromatids will remain attached.$\newline \bullet$This will prevent the segregation of chromosomes, causing a failure in the proper distribution of genetic material to daughter cells.$\newline$Therefore, if APC is defective, chromosomes will not segregate.$\newline$This corresponds to Option 2: Chromosomes will not segregate.