Question: Read this and answer the question

According to both indigenous American and European accounts and documents, American civilizations at the time of European encounter had achieved many accomplishments. For instance, the Aztecs built one of the largest cities in the world, Tenochtitlan, the ancient site of Mexico City, with an estimated population of 200,000. American civilizations also displayed impressive accomplishments in astronomy and mathematics. The domestication of maize or corn required thousands of years of selective breeding.

What had the civilizations in the Americas achieved by the time the Europeans encountered them?
Answer: many accomplishments
Question: Read this and answer the question

In 1943, Karachay Autonomous Oblast was dissolved by Joseph Stalin, when the Karachays were exiled to Central Asia for their alleged collaboration with the Germans and territory was incorporated into the Georgian SSR.

Where were the Karachays sent after their oblast was broken up?
Answer: Central Asia
Question: Read this and answer the question

Essential genes are the set of genes thought to be critical for an organism's survival. This definition assumes the abundant availability of all relevant nutrients and the absence of environmental stress. Only a small portion of an organism's genes are essential. In bacteria, an estimated 250400 genes are essential for Escherichia coli and Bacillus subtilis, which is less than 10% of their genes. Half of these genes are orthologs in both organisms and are largely involved in protein synthesis. In the budding yeast Saccharomyces cerevisiae the number of essential genes is slightly higher, at 1000 genes (~20% of their genes). Although the number is more difficult to measure in higher eukaryotes, mice and humans are estimated to have around 2000 essential genes (~10% of their genes).

What does the definition of essential genes assume an absence of?
Answer:
environmental stress