The independent African countries that signed the OAU Charter on May 25th 1963 in this context were as follows:
\(\begin{array}{c|c} & \text{Country} & \text{Year of Independence}\\ \hline 1. & \text{Togo} & \text{27th April 1960}\\ 2. & \text{Sierra leone} & \text{22nd April 1961} \\ 3. & \text{Morocco} & \text{20th March 1956} \\ 4. & \text{Angola} & \text{11th Nov. 1975} \\ 5. & \text{Chad} & \text{11the Aug. 1960} \\ 6. & \text{Gambia} & \text{18th Feb. 1965}\end{array}\)
Automatically, Angola and Gambia are ruled out in the context as they obtained independence after the charter had been signed.
Then ''A''-Togo and Sierra Leone and B-Togo and Morocco should have been considered as the correct answer on each case but that could not come true as the government of Togo was overthrown by the military on January 1, 1963. Before signing the charter on May 25th 1963, no African country had though of recognizing the military government. So it was not likely that the former head of state should be present at the meeting to sign the charter. For this reason, none of the options should be considered as the correct answer.