A rapid temperature increase about 55 mya created tropical conditions around the world, resulting in the:

a. adaptive radiation of Euprimates.
b. development of Dryopithecus.
c. spread of Sivapithecus.
d. extinction of many primate species.

a. Adaptive radiation of Euprimates.

Explanation:

Adaptive radiation is the swift diversification, from a single common ancestor, of a group of species consisting of members that exhibit a diverse array of adaptations and inhabit different ecological niches.

Climate is an important factor that determines where a species can inhabit or not. Daily and seasonal variations in temperature, annual cycles of precipitation, and larger change in climate shape adaptations of plants and animals may be considered in determining their survival. Changes in global and regional climates seemingly had profound effects on the evolutionary history and adaptive radiation of Euprimates.

A rapid temperature increase about 55 mya created tropical conditions globally that caused the adaptive radiation of Euprimates. Warm climates during the Eocene that resulted in plant diversity, created new environmental niches favorable for primates leading to the record of first major primate group: anthropoids, adapiforms, tarsiers, and omomyiforms.

this age may represent the age of the earth's accretion, of core formation, or of the material from which the earth formed. this dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.