Final answer:
Peasants were unable to build wealth primarily due to the burdensome dues owed to lords under the manorial system. These included a tithe, typically 10 percent, as well as additional labor and harvest shares, rather than the incorrect notion of a 90 percent tithe. Their servile status and legal restrictions further hindered any possibility of accumulating wealth.
Step-by-step explanation:
The most direct factor contributing to the peasants' inability to build wealth during the feudal system was the heavy dues they owed to their lords, which included both labor and a portion of what they produced. Of the options provided, the claim that peasants tithed 90 percent of what they earned is incorrect; historically, they were required to give a mandatory tax called a tithe, usually 10 percent. However, in addition to tithes, they also provided labor and a share of the harvest to the lord as part of the manorialism system. They could not generate wealth because of their bound status and these obligations, making it difficult for them to accumulate any surplus or capital.
In the manorial system, peasants worked the land and in return, they received protection and a place to live. They indeed had very limited rights and were at the mercy of the lords. Rents, various dues, and the work they had to do for the lords without pay, alongside legal restrictions such as needing the lord's permission to marry or leave the land, all restricted their ability to build wealth. Additionally, extortive practices by the rich often forced peasants off their land, and without the financial means to challenge such actions legally, they couldn't establish a secure economic base.