Which of the following is not a source of point-source pollution? a. trash dumping c. pesticide runoff b. sludge dumping d. oil spill

c. pesticide runoff

Explanation: A point source pollution is the pollution which is caused by the pollutants whose source of origin can be traced back and further pollution can be prevented. A non-point source pollution is the one which cannot be traced back to it's origin and hence, cannot be prevented from further pollution. Trash dumping, sludge dumping and oil spill are the examples of point source pollution. But pesticide runoff is the example of non-point source pollution. A surface runoff will wiped off the pesticides from their surface and discharge them to the water body the source of origin of these pesticides will remain undetermined.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.