What is the topic of this complex sentence?
after they had enjoyed fair winds and weather for a season, they were encountered many times with crosswinds, and met with many fierce storms, with which the ship was shrewdly shaken, and her upper works made very leaky; . .
a. the native americans and their ability to adapt to changing seasons
b. the mayflower sailors and their ways of predicting the weather at sea
c. the pilgrim leaders and their prayers for a safe journey across the atlantic
d. the pilgrims and the harsh weather they faced during their crossing