Statement I: Doldrums is a clam belt between 5° N and 5° S of the equator Statement I : The sun rays strike almost vertically over the equator throughout the year.

Statement I is true as the Doldrums, also known as the Intertropical Convergence Zone (ITCZ), is a belt of calm air and weak winds located approximately between 5° N and 5° S of the equator [1]. Statement II is also true because the sun's rays strike the equatorial region almost vertically throughout the year, as the subsolar point migrates only between the Tropics of Cancer and Capricorn [4]. This intense solar heating at the equator causes air to rise vertically through convection rather than moving horizontally, creating the characteristic low-pressure calm belt known as the Doldrums. Therefore, Statement II provides the correct physical explanation for the existence of the calm conditions described in Statement I, as the vertical solar insolation drives the atmospheric uplift that prevents strong horizontal surface winds.

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. [3] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 4: Climate of India > The Dynamic Concept by Flohn > p. 3
3. [4] https://oceanservice.noaa.gov/facts/doldrums.html