Answer:
four layers
Most rainforests are structured in four layers: emergent, canopy, understory, and forest floor.
Explanation:
Models are simplified representations of of different complex systems. They also help to study very small or large objects.
Option B, D and E.
Explanation:
Models are very simplified representations of complex systems and organs or structures which are prepared to study those systems by scientists and normal people easily. Many structures of human body like cells or some tissues are very small in structure or microscopic in nature. So studying them are very hard without specific instruments which are not always available. Thus models are made to easily study those structures by scientists and even normal people and students.
Here is the correct flow chart: GENE > DNA > CHROMOSOMES > NUCLEUS.
The cell nucleus contain chromosomes which are made from long DNA molecules. A gene is a short section of a DNA which codes for a specific protein.
