PLEASE HELP ASAP

A specific immune response begins when a white blood cell comes in contact with an antigen (any substance that the immune system does not recognize as part of the body). What external factor typically triggers a specific immune response?

A. an invasion of a microorganism from the external environment
B. a fluctuation of the external air pressure
C. a large release of adrenalin by the endocrine system
D. a change in the external temperature

the dark variety, as they are not visible on the dark tree barks

explanation:

ans.

dna fingerprinting is defined as a process that determines the dna characteristics of an individual. these dna characteristics are unique among individuals as their fingerprints, so it is known as dna fingerprinting.

steps of dna fingerprinting includes extraction of dna from sample, amplification of dna, restriction digestion of amplified dna, and then analysis of dna by gel electrophoresis, respectively.

thus, the next step performed by the scientist is 'to cut the amplified dna (obtained by polymerase chain reaction) by restriction enzymes that cleave the dna into fragments and their analysis.'