Option 1 suggests that both assertions are true and that the reason correctly explains the assertion. However, this isn`t the case here. There are tea plantations in Africa, which already falsifies the assertion, and tea plants do indeed require fertile soil with high humus content, that makes the reason true.

Option 2 is also incorrect because the assertion is not true, though the reason is. The reason doesn`t correctly explain the assertion in this case as there are tea plantations in Africa.

Option 3 suggests that the assertion is true and the reason is false. This is not correct as the exact opposite is true.

Therefore, option 4 is the correct answer as the assertion is false because there are indeed tea plantations in Africa, and the reason is true as tea plants do require fertile soil with high humus content.