**will mark brainliest and you**

three portions of a blood sample show clumps in anti-a serum, but not anti-b or anti-rh sera.
which blood type does the test indicate?

a. a negative (a-)

b. ab positive (ab+)

c. b negative (b-)

d. o negative (o-)

If you add a drop of anti-A serum and it clumps the blood type has blood type B markers that will fight off the A serum making the blood type B  

I got this because...  

there is A, B, AB, and O blood  

A has anti-B clumping proteins  

B has anti-A clumping proteins  

AB has no clumping proteins  

O has anti-A, anti-B, and anti-AB clumping proteins  

so the only on one with anti-A clumping proteins is blood type B  

hope this helps :)

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation: