Spines are absent in

Options

A. (a) Star fish
B. (b) sea urchin
C. (c) Brittle star
D. (d) Sea cucumber and feather star

Answer

To determine which organism among the given options lacks spines, we can analyze each option based on the characteristics of the organisms in the phylum Echinodermata.

### Step-by-Step Solution:

1. **Understand the Characteristics of Echinoderms**:
- Echinoderms are known for having a hard, calcareous endoskeleton and often possess spines on their surface. These spines serve primarily for defense.

2. **Evaluate Each Option**:
- **A. Starfish**: Starfish have spines present all over their body. They are known for their tough, spiny surface.
- **B. Sea Urchin**: Sea urchins are characterized by their numerous long spines that cover their body, providing protection.
- **C. Brittle Star**: Brittle stars also possess spines on their body, although they may be less prominent than in sea urchins or starfish.
- **D. Sea Cucumber**: Sea cucumbers have a leathery skin and an elongated body. They do not have spines, which distinguishes them from other echinoderms.
- **E. Feather Star**: Feather stars have a feathery appearance with fringes, and they also lack spines.

3. **Identify the Correct Answer**:
- From the analysis, both the sea cucumber and feather star do not have spines. However, since the question asks for the absence of spines, we can conclude that both these organisms are correct answers.

### Final Answer:
- **Sea Cucumber and Feather Star** are the organisms that lack spines.