Speed is a scalar quantity( quantity having only magnitude). So it doesn't specifies direction. Hence option C.) 5Km/hr north is incorrect.
The correct answer for the question that is being presented above is this one: "C) The reaction is spontaneous at high temperatures."
Since dH is positive and dS ~ 0 then -TdS ~ 0, meaning dG will always be greater than 0 so t<span>he reaction is spontaneous at high temperatures.</span>
You can put a known amount sodium into some sort of time release mechanism such as a pill made from soluble material. Then you can place the sodium into a calorimeter with a known mass of water and record the temperature change the water undergoes during the reaction. Then you can use the equation q(water)=m(water)c(water)ΔT to find the amount of heat absorbed by the water. since the amount of heat absorbed by the water is the amount of heat released from the sodium, q(sodium)=-q(water). Than you can use the equation q(sodium)=m(sodium)c(sodium)ΔT and solve for c(sodium)
I hope this helps and feel free to ask about anything that was unclear in the comments.