The climate on earth has changed frequently, with at least times in which earth experienced ice house conditions.
(a) two
(b) ten
(c) eight
(d) five

Five

Explanation:

The earth's climate has changed quite from the evolution of earth to its present from greenhouse earth to an Icehouse earth. There have been five known great glacial changes from Hadean, Archean, Proterozoic periods. The main factors involved in these changes are paleoclimatic events. The ice house earth is the earth as it experiences Ice age.  These are known for glacial and interglacial periods.  As the ice sheets have both occurred on poles and at regular intervals throughout the earth. There cause is generally related to CO2 and volcanic activity. Research has analyzed this using carbon dating to analyze the impact on the earth as this wave of transition began from Antarctica to arctic.  In modern times the opening of the drake passage and another example is of Indonesian seaway has given evidence to scientists of the ice house effect. And this icehouse that the earth has experienced has impacted only 20 % of the earth's history.