Prior to the Suez Canal's operation, the maritime route from Europe to India necessitated a significantly longer journey, requiring vessels to circumnavigate the southern tip of Africa via the Cape of Good Hope (Cape Town).
- The voyage commenced in London (III).
- Ships proceeded around the Cape of Good Hope (I) at Cape Town.
- The subsequent port of call after Cape Town was Mombasa (II).
- Finally, vessels arrived at Mumbai (IV), a principal Indian port during that era.
Consequently, the historical sequence of ports, preceding the Suez Canal's operational status, is: London (III), Cape Town (I), Mombasa (II), and Mumbai (IV).
Therefore, option (D) is the accurate choice.