Arrange the following living organisms from simplest (least complex) to most complex: Items: a. Amoeba b. Oyster c. Worm d. Cow Choose the correct ascending biological complexity sequence.

Introduction / Context:
Logical sequencing in biology often asks you to arrange organisms by structural/organizational complexity, typically from unicellular to more complex multicellular animals.

Given Data / Assumptions:

• Amoeba (a): unicellular protozoan.
• Worm (c): simple multicellular invertebrate.
• Oyster (b): mollusk; multicellular with specialized organs.
• Cow (d): vertebrate mammal; highly complex systems.

Concept / Approach:
Place unicellular first, then simple multicellular invertebrates, then more specialized invertebrates, and finally vertebrates/mammals.

Step-by-Step Solution:

Verification / Alternative check:
Any reversal placing oyster before worm would ignore relative organ complexity; placing cow earlier contradicts vertebrate advancement.

Why Other Options Are Wrong:

• a,b,c,d: Puts oyster before worm against typical complexity comparisons.
• Other orders reverse or scramble complexity levels.
• None of these: Not applicable because a correct ascending sequence exists.

Common Pitfalls:
Confusing ecological sophistication with biological complexity; the question is about structural organization.

Final Answer:
a, c, b, d