Basic morphology — In algal biology, the vegetative (non-reproductive) body is termed the:

Introduction / Context:
Different groups of organisms use different terms for their vegetative structures. In algae, the overall body plan—whether unicellular, colonial, filamentous, or parenchymatous—is generally referred to as a thallus.

Given Data / Assumptions:

• We are dealing with algae, not fungi or slime molds.
• “Vegetative body” means the main growth form outside of specialized reproductive structures.

Concept / Approach:
“Thallus” is the generic botanical term for an undifferentiated plant-like body lacking true roots, stems, and leaves. Algae, lichens, and some bryophytes have thalli. The alternatives—mycelium, plasmodium, and pseudoplasmodium—belong to other organismal groups and are not standard algal terms.

Step-by-Step Solution:

Verification / Alternative check:
Phycology references define algal body plans as thalli across diverse morphologies.

Why Other Options Are Wrong:

• Mycelium: filamentous fungal network.
• Plasmodium/pseudoplasmodium: slime mold stages, not algal structures.

Common Pitfalls:
Confusing cross-kingdom terminology because many groups are filamentous or sheet-like; terminology is context-specific.

Final Answer:
thallus