How many African nations have joined the International Solar Alliance (ISA) as members or signatories?

Given below are two statements, one is labelled as Assertion (A) and the other is labelled as Reason (R): Assertion (A): All the member countries of the International Solar Alliance (ISA) are strictly located between the Tropics of Cancer and Capricorn. Reason (R): The intensity of solar radiation in the tropical region is high compared to temperate and polar regions. In light of the above statements, choose the most appropriate answer from the options given below: