Normal red blood cells slide easily through narrow blood vessels. In sickle cell disease, many red blood cells change to a crescent shape like a slender moon. Crescent-shaped blood cells cause blockages in blood vessels. These blockages decrease the transport of oxygen. People with sickle cell disease often have sharp pains due to the lack of oxygen in parts of the body. Sickle cell disease is caused by an abnormal type of red blood cell gene inherited by the parents. What is the name for different forms of the same gene?
A. recessive genes
B. dominant genes
C. traits
D. alleles

answer; i believe that the correct answer is (a); a large rock being weathered by wind and rain;

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water pollution kills aquatic life. aquatic life includes algae and other plant life that use photosynthesis. photosynthesis takes   c02 out of the air.  

c02is a greenhouse gas.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.

water and alcohols have similar properties because water molecules contain hydroxyl groups that can form hydrogen bonds with other water molecules and with alcohol molecules, and likewise alcohol molecules can form hydrogen bonds with other alcohol molecules as well as with water.