One feels that there . . . . . . . . any noticeable improvement in the human rights problem in Africa until all the African countries . . . . . . . . their economic difficulties.

In the given sentence "One feels that there cannot be any noticeable improvement in the human rights problem in Africa until all the African countries will overcome their economic difficulties," the correct tense forms to fill in the blanks are "cannot be" and "will overcome."

"there cannot be any noticeable improvement" - The phrase "cannot be" is in the present tense and indicates that a noticeable improvement in the human rights problem in Africa is not possible at the moment.

"until all the African countries will overcome their economic difficulties" - The phrase "will overcome" is in the future tense, expressing a future action that is expected to happen. It shows that the African countries need to resolve their economic difficulties in the future for any improvement in the human rights problem to occur.

Both the present tense "cannot be" and the future tense "will overcome" are appropriate here to convey the cause-and-effect relationship between the economic difficulties and the improvement in human rights.

The other options do not use the correct tense forms for the given sentence. Option B, "hasn't been/had overcome," uses the present perfect and past perfect tenses, which do not fit the context of the sentence. Option C, "won't be/overcome," combines the future tense with the present tense, which is not grammatically correct. Option D, "wouldn't be/would be overcome," uses the past conditional and past tense, which is not appropriate for describing a future event. Option E, "wasn't/have overcome," uses the past tense and present perfect tense, which are not suitable in this context.

Therefore, the correct answer is "A. cannot be/will overcome.