C. the answer is c. i just took this test on keystone (i think this is keystone question. right?0
1. Testing only one variable
A controlled variable means its the one that stays the same. In a controlled experiment, it means there is only one manipulated, (changed) variable.
Answer:
Ependymal cell present in the central nervous system has an important role in production and control of cerebrospinal fluid (CSF). This ciliated cell acts as sensory for coordination to cellular signaling in the production and control of CSF.
Explanation:
Am certain that the factor that prevents us from finding fossils from the Precambian era is that Most rocks from that era are deeply buried. The precambrian is the informal name for the large expanse of time preceding the current Phanerozoic Eon. It began with the Earh's Formation about 4.5 billion years ago and lasted until the advent of multicellular life about 542 million years ago.
Alright bud the best answer to this question would be that one of the first scientists of the Renaissance to advance taxonomy through first hand observations was Cordus
