That would be ascomycota or sac fungi. Sac fungi are characteristically known for producing ascus. This is a sac-like structure that contains haploid spores called ascospores. Some examples of sac fungi are yeast, truffles, morels and dead man's fingers.
A dichotomous key is defined as a biological tool for identifying unknown organisms to a particular taxonomic level. It is constructed with many levels and series of couplets.
So, by observing the given dichotomous key, it is concluded that the correct answer is Option A- Organism X and Z have at least one observable trait in common in this dichotomous key.
