Core cellular features — Which structures do all true algae (eukaryotic algae) possess?

Introduction / Context:
Algae, as used in eukaryotic phycology, are photosynthetic eukaryotes distinct from cyanobacteria (which are prokaryotes). Understanding what structures all true eukaryotic algae share is fundamental to cell biology and taxonomy.

Given Data / Assumptions:

• The term “algae” here refers to eukaryotic lineages (green, red, brown algae, diatoms, etc.).
• Cyanobacteria are excluded because they are bacteria (prokaryotic) and lack a nucleus.
• Chloroplasts in algae are plastids derived from endosymbiosis and carry pigments.

Concept / Approach:
All eukaryotic algae possess membrane-bound nuclei. They also possess plastids (chloroplasts) responsible for photosynthesis. While some specialized parasitic or colorless algal forms may be secondarily non-photosynthetic, they typically retain plastids or plastid remnants consistent with algal ancestry. For standard educational purposes, nuclei and chloroplasts are considered universal features among true algal groups.

Step-by-Step Solution:

Verification / Alternative check:
Comparative cell biology texts show eukaryotic algal cells with nuclei and plastids; prokaryotic “algae” (cyanobacteria) are excluded by definition in modern usage.

Why Other Options Are Wrong:

• (a) or (b) alone is incomplete since both features are characteristic.
• (d) contradicts core cell biology.

Common Pitfalls:
Confusing algae with cyanobacteria; the latter lack nuclei and chloroplasts and should not be grouped with eukaryotic algae in this context.

Final Answer:
Both (a) and (b)