The activation of helper T cells is likely Group of answer choices in the bone marrow during the self-tolerance test. when an antigen is displayed by a dendritic cell. when B cells respond to T -independent antigens. when natural killer (NK) cells come in contact with a tumor cell. when a cytotoxic T cell releases cytokines.

Which short-term environmental changes would a very small asteroid or comet impact on earth most likely cause? check all that apply. flooding extinction craters on surface changes in weather patterns death of organisms and populations

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.

Which of the following may one conclude from a map that shows the average ph value of rainfall in the u. s.? acid rain is a more serious problem on the east coast. acid rain falls equivalently across the continental u. s. there are more factories on the west coast. the midwest has fewer forests than the rest of the u. s.