D). Carcinogens are chemical factors in an organism's environment that can cause spontaneous mutation.
An average person (let's say one that weights 70 kg) has about 5.5 liters of blood (that's a little more than 160 ounces or 1.2 to 1.5 gallons). Other way of saying this is : about 7% of body weight.
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i think it's D I hope this helps :)
