Final answer:
Cytochalasin D blocks the plus ends of actin filaments, allowing depolymerization at the minus ends, affecting cellular processes like motility and division.
Step-by-step explanation:
The chemical known for blocking the plus ends of actin filaments and allowing depolymerization at the minus ends is Cytochalasin D. Unlike the other chemicals listed, Cytochalasin D specifically inhibits the addition of new monomers to the growing plus end of an actin filament, while depolymerization can continue unhindered at the minus end. This selective inhibition affects the dynamic equilibrium of actin polymerization and depolymerization that is crucial for many cellular processes such as cell motility, muscle contraction, and cell division.