28. Which of the following statements are accurate?

A. none of the answers are correct

B. An effective humoral immune response typically requires both T cell and B cell activation.

C. T cells activation does not usually require antigen presentation by an antigen presenting cell.

D. Viruses can avoid activating the adaptive immune system if they do not change their surface antigens once they have been recognized by T and B cells.

E. People who were affected with the smallpox virus before cowpox virus were naturally immune to the smallpox virus because the viruses shared some common antigens and the memory cells that recognized cowpox antigens responded to smallpox antigens as well.

F. Helper T cells can kill cells that are infected with viruses and Cytotoxic T cells are known to activate B cells.

Asap what occurs after cytokinesis is completed at the end of meiosis 1?

How does deforestation affect the water cycle? a. it increases the amount of runoff b.it increases the amount of percolation c. it increases the amount of transpiration d. it increases the amount of precipitationa it increases the amount of runoff

Rease is an enzyme used by plants to break down urea (a nitrogen-containing compound) into carbon dioxide and ammonia. urease urea > > > carbon dioxide and ammonia ammonia is broken down by plants into a nitrogen source plants need to grow. thus, plants could not use urea as a nitrogen source unless it was first converted to ammonia. in soybean plants there are two different kinds of urease, one produced in the seeds and the other produced in the leaves of the plant. three types of soybean plants were used in a set of experiments: normal soybeans and two mutant strains, one lacking the urease in the seeds only (strain 1) and one lacking urease in the leaves only (strain 2). experiment 1 separate areas in a field were planted with normal, strain 1, and strain 2 soybeans. all types of soybeans appeared to grow, flower, and produce seeds equally well. there were no externally detectable differences among the strains. experiment 2 small pieces of plant leaves of equal weight were obtained from each type of soybean plant and separately placed on media in culture dishes. tissue growing in this way will become an unorganized clump of cells referred to as callus. to provide a controlled nitrogen source, half the tissue samples of each type were placed on media containing urea, and the other half of the samples were placed on media containing ammonia. after 30 days, the weight gain for each of the callus samples was determined. results are shown in the table below.