The correct answer to the question is option 1: A-2, B-3, C-4, D-1. This answer correctly matches each country with its respective president during a specific time period. The breakdown of the answer is as follows:

A. Congo-2: Joseph Kabila was indeed the President of the Democratic Republic of Congo from 2001 to 2019.

B. Nigeria-3: Olusegun Obasanjo served as the President of Nigeria from 1999 to 2007.

C. Uganda-4: Yoweri Museveni has been the President of Uganda since 1986.

D. Zambia-1: Levy Mwanawasa was the President of Zambia from 2002 to 2008.

Option 2, 3, and 4 do not provide the correct matches between the countries and their respective leaders. For example, option 2 suggests that Olusegun Obasanjo was the president of Congo, which is incorrect. The same applies to the other mismatched options.