The answer is B. We don't always have exact proof but our observations tell us more than we already know.
I'm pretty sure it's <span>both. Allopatric speciation occurs when there is a physical barrier formed like a mountain or river. and Sympatric speciation occurs when there is a genetic barrier formed like a mutation that causes a different mating season or preference in mate choice.
hope this helps!</span>
Answer:
Five hundred out of every one thousand rats would die
Explanation:
Median lethal dose LD-50 (lethal dose 50%) is used as a measure of poisoning potential of a substance. LD-50 is the dose of substance, given all at once, which causes the death of 50% (one half) of a group of test animals. LD-50 is usually expressed as the amount of chemical administered (e.g., milligrams) per 100 grams or per kilogram of the body weight of the test animal. In this example, the test animals were rats, they were administrated a certain insecticide. Administration methods that are the most common are dermal (applied to the skin) and oral (given by mouth). If the determined LD-50 is 250 milligrams per kilogram of body mass, it means that one half (five hundred) of one thousand rats would die, because we are talking about lethal doses.
