Oxygen and carbon dioxide travels to and from tiny air sacs in the lungs, through the walls of the capillaries, into the blood. Blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs.

Sunlight is the main energy source
Answer:
3. Household wastes
2. Landfills
1. Agriculture
Explanation:
The groundwater is more and more contaminated, and there are numerous ways in which the contamination occurs. The causes of pollution mainly come from the human activities. The humans use all sorts of chemicals, fossil fuels, paints, and often there is waste from them, waste that is dumped into the drainage, and occasionally reaches the groundwater. The leaking of linings also manages to cause lot of damage, as very often it can reach the groundwater, causing heavily contamination of it. The agriculture, as much as it is needed, is a big polluter too, and the pollution mainly comes from the usage of pesticides, herbicides, and fungicides, which wash through the soil and end up in the groundwater.
B they were given additional dities
Answer:
. The main structural differences between plant and animal cells are the additional structures found in plant cells. These structures include: chloroplasts, the cell wall, and vacuoles. In animal cells, the mitochondria produces the majority of the cells energy from food.