The continent having the largest area in the equatorial belt is

The equatorial belt is generally defined as the region between 10° N and 10° S latitudes, characterized by the equatorial low-pressure system and the Intertropical Convergence Zone [2]. Africa is the only continent through which the Equator, the Tropic of Cancer, and the Tropic of Capricorn all pass, with the Equator running almost through its center. While the equatorial climate has significant extents in the Amazon (South America) and the East Indies (Asia), Africa is described as being wide in its equatorial region compared to the narrow equatorial landmass of South America [3]. Africa's massive landmass is the second largest globally, and its central position on the Equator ensures it possesses the largest total land area within the 10° N to 10° S equatorial belt compared to the tapering landmass of South America or the fragmented islands of equatorial Asia.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Equatorial Low-Pressure Belt or 'Doldrums' > p. 311
2. [2] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 14: Climate > Pressure and Planetary Winds > p. 139
3. [3] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 15: The Hot, Wet Equatorial Climate > Distribution > p. 150