What factor prevents us from finding fossils from the Precambrian era? A. Life-forms in this era had no skeletons.
B. This was before life existed on Earth.
C. Life was destroyed by a series of mass extinctions.
D. There are no rocks left from that era.

Consider the classification levels of a human. eukarya ,animalia ,chordata ,mammalia ,primates, hominidae ,homo ,sapiens .which is the most specific taxonomic level in the classification system above? a sapiens b homo c hominidae d primates

Aresearcher designed an investigation to test what effect eating different types of food would have on blood insulin levels. she selected 10 male subjects who were all 25 years of age and in good health. the experiment took place over 3 days. at 8: 00 a.m. on each day, the subjects ate a meal consisting of only 1 type of food. they had their blood insulin levels measured after consuming the meal. on day 1 they ate a high fat diet, on day 2 they ate a high protein diet, and on day 3 they ate a high sugar diel what is the independent variable in this experiment? a the age of the subjects b the blood insulin level c the type of food consumed d the time of day the meal was consumed

Astudent measured the amount of carbon dioxide (co2) produced by yeast during an experiment. use the data in the table at the right to answer the questions below. which variable is the dependent variable?