When a country has a strong currency, generally its export decreases – this is the answer to the first question.

Imagine, a tone of rice costs 100 dollars, that is 100 pounds. With a strong dollar, it’s 120 pounds now – the British will be able to afford less of US rice now!
About the second question – I think that if neither has an absolute advantage, this also likely means that neither has more natural resources.

now, country A exports milk to country B, which means that it’s cheaper to produce milk in the country A. Therefore, the answer “The opportunity cost of producing milk is lower for Country A” is correct.