Final answer:
To determine if two quadrilaterals are similar, compare their angles and side lengths.
Step-by-step explanation:
To determine whether quadrilateral EFGH is similar to quadrilateral QRST, we need to compare their corresponding angles and side lengths.
If the corresponding angles of two quadrilaterals are congruent and the corresponding side lengths are proportional, then the quadrilaterals are similar.
Since the question does not provide any information about the angles or side lengths of EFGH and QRST, it is impossible to determine whether they are similar. Therefore, the correct answer is C) Impossible to determine.