Numerical taxonomy - All observable characteristics
Numerical taxonomy is a method of classifying organisms based on their observable characteristics. It involves the collection and analysis of quantitative data related to various traits or characteristics of organisms. This data is then used to create numerical codes or matrices, which are used for constructing dendrograms or similarity trees. The observable characteristics can include morphological, physiological, biochemical, or behavioral traits.

Cytotaxonomy - Cytological information
Cytotaxonomy is a branch of taxonomy that focuses on the study of the cellular characteristics of organisms. It involves the examination of the number, structure, and behavior of chromosomes, as well as other cellular components such as cell organelles. Cytotaxonomy provides valuable information for understanding genetic relationships, species identification, and evolutionary patterns.

Chemotaxonomy - Chromosome number and structure
Chemotaxonomy is a method of classification that is based on the chemical composition of organisms. It involves the analysis of chemical compounds present in organisms, such as lipids, proteins, carbohydrates, nucleic acids, and secondary metabolites. These chemical markers can provide insights into the evolutionary relationships and systematic classification of organisms. Chromosome number and structure are not directly related to chemotaxonomy, as it mainly focuses on chemical compounds.

Cladistic taxonomy - Origin from a common ancestor
Cladistic taxonomy is a method of classification that is based on evolutionary relationships and the concept of common ancestry. It involves the identification and analysis of shared derived characteristics, known as synapomorphies, among different groups of organisms. By constructing cladograms or phylogenetic trees, cladistic taxonomy aims to depict the evolutionary history and relatedness of organisms. The origin from a common ancestor is a fundamental principle of cladistic taxonomy.

Explanation:
The incorrect pair in this question is option C, which states that chemotaxonomy is based on chromosome number and structure. However, chemotaxonomy is actually based on the chemical composition of organisms, including the analysis of various chemical markers. Chromosome number and structure are not directly related to chemotaxonomy. This makes option C the incorrect pair.