Answer:
The question does not fit the options, since the options all refer to a 2% interest rate in US dollars and a 6% interest rate in euros. While the question states that the interest rate in US dollars is 5% and the interest rate in euros is 4%.
The answer to the question is:
If you borrow $1,000,000 today, you will be able to purchase 800,000€. Or if you borrow 800,000€ today, you will be able to purchase $1,000,000.
Since the forward rate is higher, you should borrow dollars, invest in euros and after a year, purchase back dollars and pay back your debt.
Gain:
= 800,000€ x 1.04 = 832,000€ x 1.4 = $1,164,800, then you pay back your loan = $1,164,800 - ($1,000,000 x 1.05) = $1,164,800 - $1,050,000 = $114,800 gain
Options C will also yield gains:
option C = borrow 800,000€ and buy $1,000,000. After one year you will have $1,020,000 which you can use to purchase 850,000€. Your gain = 850,000€ - (800,000€ x 1.06) = 2,000€