Why are drift nets a problem?
a. they are too expensive to be practical.
b. they are not big enough to catch many fish.
c. they are too big and hard to manage.
d. they can accidentally catch dolphins and turtles.

The correct answer is option D.

Explanation:

The free-flowing nets used in oceans to catch fish by their gills are known as drift nets. A net can have a dimension of up to 15 meters deep and 89 kilometers in length. These nets are not selective in nature, as various fishes comprising marine mammals can get trapped in them.  

It can trap turtles, sharks, dolphins, and seabirds. These unwanted organisms are withdrawn from the nets and are thrown back dead by the fisherman into the ocean. The drift nets are an extremely destructive fishing technique and are also banned in various parts of the world.  

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