Which of the following is a biotic factor that could reduce a population of frogs

a: water pollution from chemical fertillizers

b: drought that dries up ponds and puddles

c: an increase in aquatic bird population

d: a decrease in parasitic flukes

C.

Biotic mean alive, so we can cut off the first 2 easily. Aquatic birds eat frogs, so that one is safe for now. A decrease in something parasitic usually helps the population, so D is out too. The only one left is C.

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.