Final answer:
The extracellular matrix controls cell growth by providing structural support and initiating signaling cascades that modulate gene expression and can induce apoptosis when a cell loses contact.
Step-by-step explanation:
The extracellular matrix (ECM) plays a critical regulatory role in cell growth by providing structural support and initiating a signaling cascade when cells bind to it. This signaling is crucial in maintaining proper cell positioning and preventing cells from traveling and proliferating uncontrollably, which can lead to metastasis in cancer. When cells detach from the ECM, the absence of these signals can trigger apoptosis, the programmed cell death, as a fail-safe against uncontrolled cell growth and metastasis. Thus, in response to how the ECM controls the growth of cells, option b) Modulates gene expression would be a suitable answer as it suggests the ECM through signaling can influence the expression of genes involved in cell growth and division.