Centriole is

Options

A. Microtubular and membraneless
B. Absent in Amoeba, red algae, blue-green algae, conifers, and angiosperms and is made up of peripheral triplet microtubules
C. Basically locomotory and their role in spindle formation is secondary
D. All of the above

Answer

### Step-by-Step Solution:

1. **Definition of Centriole**: A centriole is an organelle found in eukaryotic cells. It plays a crucial role in cell division and organization.

**Hint**: Remember that centrioles are specific to eukaryotic cells and are not found in prokaryotic cells.

2. **Membrane Structure**: Unlike many other organelles in eukaryotic cells, centrioles are not membrane-bound. This means they do not have a surrounding membrane like other organelles such as the nucleus or mitochondria.

**Hint**: Think about how most organelles are surrounded by membranes, but centrioles are an exception.

3. **Cylindrical Structure**: Centrioles have a cylindrical shape and are primarily composed of microtubules. Microtubules are structural components that help maintain cell shape and are involved in various cellular functions.

**Hint**: Visualize the structure of centrioles; they look like small tubes or cylinders.

4. **Role in Cell Division**: Centrioles are crucial for the formation of the spindle fibers during cell division (mitosis and meiosis). They help in the proper segregation of chromosomes.

**Hint**: Remember the role of centrioles in organizing the spindle apparatus during cell division.

5. **Formation of Basal Bodies**: In some organisms, centrioles can also form basal bodies, which are structures that anchor cilia and flagella. Cilia and flagella are important for the movement and locomotion of certain cells and organisms.

**Hint**: Consider how centrioles contribute indirectly to movement through their role in forming structures like cilia and flagella.

6. **Absence in Certain Organisms**: Centrioles are absent in certain organisms, such as amoeba, red algae, and blue-green algae. This highlights that not all eukaryotic cells contain centrioles.

**Hint**: Keep in mind that while centrioles are common in many eukaryotes, there are notable exceptions.

### Summary:
Centriole is a cylindrical, membrane-less organelle found in eukaryotic cells, composed of microtubules, involved in spindle formation during cell division, and can form basal bodies for cilia and flagella. They are absent in certain organisms like amoeba and some algae.