A multicellular, filamentous alga exhibits a type of sexual life cycle in which the meiotic division occurs after the formation of zygote. The adult filament of this alga has

Options

A. haploid vegetative cells and diploid gametangia
B. diploid vegetative cells and diploid gametangia
C. diploid vegetative cells and haploid gametangia
D. haploid vegetative cells and haploid gametangia

Answer

To solve the question regarding the multicellular, filamentous alga with a specific sexual life cycle, we need to analyze the information provided step by step.

### Step-by-Step Solution:

1. **Understanding the Life Cycle**: The question states that the alga exhibits a sexual life cycle where meiotic division occurs after the formation of the zygote. This indicates that the alga undergoes zygotic meiosis.

2. **Formation of Zygote**: The zygote is formed by the fusion of male and female gametes. Since gametes are haploid, the zygote is diploid.

3. **Meiotic Division**: After the zygote is formed, it undergoes meiosis. Meiosis is a reduction division that produces haploid spores from the diploid zygote.

4. **Spores and Adult Filament**: The haploid spores produced from meiosis will then undergo mitotic divisions to develop into the multicellular filamentous structure of the alga. Therefore, the adult filament is composed of haploid cells.

5. **Gametangia Formation**: Gametangia are the organs that produce gametes. Since the adult filament is haploid, the gametangia that produce the male and female gametes will also be haploid.

6. **Conclusion**: The adult filament of this alga consists of haploid vegetative cells and haploid gametangia. The only diploid stage in this life cycle is the zygote.

### Final Answer:
The adult filament of this alga has **haploid vegetative cells and haploid gametangia**.