To reduce the risks of cross contamination when performing cpr, we should try, as far as possible, and if conditions permit, practice cpr in a clean environment of any chemical or physical waste, that the person who is performing the procedure doesn´t have any respiratory disease that can make the situation worse, having clean hands not to contaminate the patient, keep other people away so fresh air can flow freely.
They travel at the same speed.
Density dependent factors are the aspects of the environment that limit a population's growth regardless of the density of the population. So in this case, the answer is hurricanes.
It is false. Human cells do not have a cell wall in the same way that plants do.