Final answer:
The land bridge is exposed above sea level during ice ages in the Quaternary Period, such as Beringia during the most recent ice age.
Step-by-step explanation:
The land bridge is exposed above sea level during periods of lower sea levels, specifically during the ice ages of the Quaternary Period. These ice ages caused a significant drop in sea levels as water was frozen in glaciers, creating land bridges between continents. For example, during the most recent ice age, a land bridge called Beringia connected modern-day Alaska and Russia.