Final answer:
The British steamship line known for the Queen Mary and Queen Elizabeth is the Cunard Line, which was established in 1840 and named after Sir Samuel Cunard.
Step-by-step explanation:
The legendary British steamship line that included the Queen Mary & the Queen Elizabeth is named after a British baronet, Sir Samuel Cunard. The correct answer to the question is: b) Cunard Line.
The Cunard Line was established in 1840 and quickly became a leading operator of passenger ships. Its reputation for safety and speed made it a favorite among Atlantic travelers, and it is well-known for the impressive ships it has operated over the years, including the aforementioned Queen Mary and Queen Elizabeth, as well as the Queen Elizabeth 2 and the current flagship, the Queen Mary 2.