Cells become specialised to carry out a specific role and then they become a group of tissues and the group of tissues work together become an organ and the a group of organs become 1 system
Sulfur dioxide<span> and </span>nitrogen oxide mix <span>with the water molecules in the atmosphere to produce acidic rain </span>
<span>In aquatic ecosystems net primary productivity is related to</span>available sunlight and nutrients.
Answer:
The correct answer is D. Umbilical cord
Explanation:
The umbilical cord connects the fetus to the placenta and through it exchanges nutritional substances as well as oxygen-rich blood. The umbilical cord is maintained throughout gestation until the moment of birth, when it is cut and leaves a permanent scar, the navel. The umbilical cord is responsible for breathing and feeding the fetus until the moment it is born, so any failure or blockage in the circulation of oxygen and nutrients through the cord can lead to injury or even death of the embryo. It also serves to remove waste and carbon dioxide (CO2).