Final answer:
If heterochromatin spreads inappropriately into an area with active genes, it can lead to the silencing of those active genes.
Step-by-step explanation:
If heterochromatin spreads inappropriately into an area with active genes, it can lead to the silencing of those active genes (option A). Heterochromatin is tightly packed and contains genes that are not expressed, while active genes are found in the less compact euchromatin. When heterochromatin spreads into an area with active genes, it can cause the genes to become inaccessible to the transcription machinery, resulting in their silencing. This can have significant effects on cellular processes and can lead to various disorders and diseases.