Answer:
One
Explanation:
In a controlled experiment only one variable is changed at a time, while the others are kept the same/controlled so changes can be observed and a causation can be determined.
Answer:
a long rodlike structure that develops dorsal to the gut and ventral to the neural tube. The notochord is composed primarily of a core of glycoproteins that are encased in a sheath of collagen fibers wound into two opposing helices.
D.A decreased mental ability and uncontrollable movements
Answer:
C
Explanation:
In 1839, Theodore Swhwann, a German Zoologist examined bits of animals under a microscope and observed that animals were composed of cells.
