Arnold is reviewing the Miller-Urey experiment and similar experiments on the origins of life on Earth. In each of these experiments, several
inorganic gases were mixed in a chamber to simulate the atmosphere of early Earth. Then the gases were subjected to a spark of electricity,
which simulated a lightning bolt. The gases reacted to form simple amino acids and other organic compounds.
Arnold claims that the results of the experiments show how the first organic molecules formed on Earth
Which statement is the best evaluation of Arnold's claim?
A The claim is well justified. The results were verified by many experiments
B. The claim is well justified. The experiments tested all of the possible mechanisms for making organic molecules.
C. The claim is poorly justified. The experiments tested only one mechanism for making organic molecules; other mechanisms may exist.
D The claim may or may not be justified, depending on the conclusions of the scientists who completed the experiments.

Ayoung boy has been found and police are trying to locate his family they take a dna sample from him and begin collec dna samples from families who have missing children if police use dna samples only from the fathers, which type of dn technology can they use to identify the boy's parent? y-chromosome analysis omtdna (mitochondrial dna) analysis vntrs (variable tandem repeats) o pcr (polymerase chain reaction) analysis

Rease is an enzyme used by plants to break down urea (a nitrogen-containing compound) into carbon dioxide and ammonia. urease urea > > > carbon dioxide and ammonia ammonia is broken down by plants into a nitrogen source plants need to grow. thus, plants could not use urea as a nitrogen source unless it was first converted to ammonia. in soybean plants there are two different kinds of urease, one produced in the seeds and the other produced in the leaves of the plant. three types of soybean plants were used in a set of experiments: normal soybeans and two mutant strains, one lacking the urease in the seeds only (strain 1) and one lacking urease in the leaves only (strain 2). experiment 1 separate areas in a field were planted with normal, strain 1, and strain 2 soybeans. all types of soybeans appeared to grow, flower, and produce seeds equally well. there were no externally detectable differences among the strains. experiment 2 small pieces of plant leaves of equal weight were obtained from each type of soybean plant and separately placed on media in culture dishes. tissue growing in this way will become an unorganized clump of cells referred to as callus. to provide a controlled nitrogen source, half the tissue samples of each type were placed on media containing urea, and the other half of the samples were placed on media containing ammonia. after 30 days, the weight gain for each of the callus samples was determined. results are shown in the table below.

2. which is the last step in the scientific method?