Which of the following is the oldest tennis tournament in the world?

The correct answer is B, Wimbledon. The Championships were first played at the All England Lawn Tennis and Croquet Club in London in 1877, which makes Wimbledon the oldest tennis tournament in the world. That first edition had only a gentlemen's singles event; the ladies' singles was added in 1884.

Option A, the US Open, began in 1881 as the US National Championship, four years after Wimbledon, and is the second oldest of the four. Option C, the French Open, dates from 1891 but stayed a national event, open only to members of French clubs, until 1925, so it is often shown as the youngest in international terms while still older than the Australian event. Option D, the Australian Open, was first held in 1905 as the Australasian Championships and is the newest of the four. Fixing the order 1877, 1881, 1891, 1905 in memory settles every question of this kind.