By "ascending order", they mean the exponents for the variable, which is t in all of these. Ascending means increasing, so you want to start with your constant (number only) value, then the t term, then the t2 term, and t3 after that, if there are that many terms.
The only one that fits this pattern is D.
Note that A is in descending order, which is the standard order. But in this case, they are looking for D.
