A population of 100 butterflies living on an acre of land loses three-quarters of its members when a sudden freeze in the spring occurs just after they emerge as caterpillars. This population has undergone a reduction in population size due to

The correct answer is - a density independent factor.

Explanation:

Any external cause or change that leads to the change in the size of a population regardless of the density of the particular population known as a density independent factor in ecology.

Density independent factors are the factors that are not affected by the size of the population size of the species such as weather, climate and natural disasters.

Thus, the correct answer is -  a density independent factor.

halogen, any of the six nonmetallic elements that constitute group 17 (group viia) of the periodic table. the halogen elements are fluorine (f), chlorine (cl), bromine (br), iodine (i), astatine (at), and tennessine (ts).

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.