If i remember correctly, the question was asking for
1 year rate - 2 years from now, so it would be calculated based on
(1+3-yr spot rate)^3 = (1+2-yr spot rate)^2 x (1+X)
so it it ends up to be 6.4
But if you have to take a guess, the 1 yr rate 2 years from now would be noticeably higher than the previous rates since the first two years, rates are low, which leaves the first two choices out (both are below 5.7 i think) and 6.1 just aint high enough to compensate the first two years.