Question 3 of 20 :
Select the best answer for the question.
3. Sickle-cell anemia is caused by a
mutation in the gene encoding
hemoglobin, causing red blood cells
to appear
na oborinal

answer; ///(b) it is composed of four protein chains and four heme groups;

i think the answer would d

answer:

convection currents in the magma drive plate tectonics. heat generated from the radioactive decay of elements deep in the interior of the earth creates magma (molten rock) in the aesthenosphere. the aesthenosphere (70 ~ 250 km) is part of the mantle, the middle sphere of the earth that extends to 2900 km.