Agaricus belogs to basidiomycetes where basidiospores are produced exogenously after karyogamy ,in neurospora sexual spores are produced endogenously.

Explanation:

Introduction:
Karyogamy is the fusion of two haploid nuclei to form a diploid nucleus. This process occurs after the fusion of two haploid gametes or cells during sexual reproduction. Meiosis, on the other hand, is a specialized cell division process that results in the formation of haploid cells called spores. These spores are capable of developing into new organisms under suitable conditions.

Spore Production:
After karyogamy, the diploid nucleus undergoes meiosis, which results in the formation of haploid spores. These spores are produced exogenously, which means they are released outside the parent organism. This is in contrast to endogenous spore production, where spores are formed and retained within the parent organism.

Options:
a) Neurospora: Neurospora is a genus of fungi that reproduce both sexually and asexually. However, spores in Neurospora are produced endogenously, within specialized structures called ascus. Therefore, option a is incorrect.

b) Alternaria: Alternaria is a genus of fungi that mainly reproduce through asexual spore production. These spores, called conidia, are produced exogenously on specialized structures called conidiophores. Therefore, option b is incorrect.

c) Agaricus: Agaricus is a genus of mushrooms that reproduce sexually. After karyogamy, the diploid nucleus undergoes meiosis, resulting in the formation of haploid spores. These spores are produced exogenously on specialized structures called basidia. Therefore, option c is correct.

d) Saccharomyces: Saccharomyces is a genus of yeast that reproduces mainly through asexual budding. Bud formation in Saccharomyces does not involve karyogamy and meiosis, and hence, spores are not produced in this manner. Therefore, option d is incorrect.

Conclusion:
After karyogamy followed by meiosis, spores are produced exogenously in Agaricus. This process occurs on specialized structures called basidia. Neurospora, Alternaria, and Saccharomyces do not follow the same reproductive process, and hence, spores are not produced in a similar manner.