There are many different categories of t-cells that carry out various roles for the immune system. differentiation for most t-cells occurs during the t-cell maturation, but some differentiation occurs after maturation following antigen presentation. one category of t-cells functions in antigen presentation and activation of b cells, as well as the activation of cytotoxic t-cells and macrophages. what is this category of t-cell? a) t b) memory t c) regulatory t d) natural killer t

The phylogenetic tree illustrates the relationship between humans and our closest living relatives. the tree was based on biochemical comparisons, including dna and amino acid sequences. according to the biomolecular data, we could infer that a) the four organisms do not have a common ancestor. b) humans are more closely related to chimps than any other apes. c) chimps are more closely related to gorillas than they are to humans. eliminate d) there is no evidence if any relationship between the four branches on the tree.

The distant ancestors of tigers may have had bodies without stripes. use the theory of natural selection to explain how tigers may have evolved to have stripes.

With regard to enzymes, key is to lock as a) substrate is to activation energy eliminate b) product is to substrate. c) enzyme is to active site. d) substrate is to active site.