**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 :)

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.