What produces Earth's magnetic field?

Which element forms the basis of all organic organisms a carbon b oxygen c hydrogen d nitrogen

Plz genetic engineering can be applied to many fields including medicine and agriculture. which of the following is a medical application of genetic engineering? a. giving crop plants recombinant dna so that they would be resistant to herbicides. b. examining a persons pedigree to determine whether they can carry a gene for a genetic disease. c. analyzing a persons dna to see how closely they are related to another person. d. certain genes into bacteria so that they will produce a needed medicine.

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?