In the structure of dna, which nucleotides always pair with adenine

The distribution of related animals and plants across the world

Which statement is the best summary of the model? a-a series of aerobic and anaerobic reactions take place in cells b- the sun's energy moves through trophic levels in a food chain c-light energy is converted into stored chemical energy plants.d- food molecules are broken down in the cells if living things.

What is any method of measuring the age of an object or event in years, such as using atomic half-life?