Final answer:
Commodore A) Cornelius Vanderbilt left less than 5% of his fortune to his second wife and daughters, giving the majority to his son, reflecting common inheritance practices of his time.
Step-by-step explanation:
The "commodore" who left less than 5% of his $100 million fortune to his second wife and 8 daughters, with the majority going to his son was Cornelius Vanderbilt (Option A). Known for his significant industrial contributions to the railroad industry, Vanderbilt was one of the richest Americans of his day. His methods of consolidating several smaller railroad lines to create the powerful New York Central Railroad Company made him a central figure in the transformation of the American economic landscape during the post-Civil War era. However, upon his death in 1877, Vanderbilt left the vast majority of his immense wealth to his son, in line with the business practices of that era that favored male heirs.