<span>1 archaic : happy, pleased
2 archaic : inclined, desirous
3 a : willing
he was very fain, for the young widow was “altogether fair and lovely … ” — Amy Kelly
b : being obliged or constrained : compelled
Great Britain was fain to devote its whole energy … to the business of slaying and being slain — G. M. Trevelyan</span>
I would say that the best theme to address those key points listed, would be: A. Feeling hopeless is unreasonable when faced with challenges. In other words, we shouldn't feel as if the end of that world is at hand, just because challenges and tests come our way. That is to be expected. Hope that helps.
D
Because opportunity cost is a benefit profit or value that firm has to give up in order to achieve or have something else
1) closeness 2) Overseas
3) Impossibility
4) Amazingly
5) Clarity
6) Transmit
