B and E are out because we do not know what 'they' refers to.
Now the choice is between A, C and E.
I did not choose A since it seemed to me to be bit wordy and confusing.
Now the choice is between B and D.
The catch point here are the words 'intention to' and 'intend'.
The real meaning of 'intend' is 'to mean or signify'.
So what is meant to sustain the future? Its the fund.
hence I went by C as it seems to be more direct and concise than D is.
Moreover, your simplified sentence sounds better if you say
Alaska deposits money intended(meant
) to save its future.
What do you say?
Let me know if there are better explanations.
A 750 aspirant.