Step 1: Garden pea (Pisum sativum) is linked to Mendel's laws of inheritance. Step 2: Four o'clock plant shows incomplete dominance; Neurospora established the one-gene-one-enzyme concept. Step 3: Sweet pea demonstrates complementary gene action. \[ \boxed{\text{(A)-(III), (B)-(I), (C)-(II), (D)-(IV)}} \]